Patterned transparent conductors and related manufacturing methods

ABSTRACT

A patterned transparent conductor includes a substrate and additives at least partially embedded into at least one surface of the substrate and localized adjacent to the surface according to a pattern to form higher sheet conductance portions. The higher sheet conductance portions are laterally adjacent to lower sheet conductance portions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/527,069, filed on Aug. 24, 2011, U.S. Provisional Application No.61/536,985, filed on Sep. 20, 2011, U.S. Provisional Application No.61/537,514, filed on Sep. 21, 2011, U.S. Provisional Application No.61/539,415, filed on Sep. 26, 2011, U.S. Provisional Application No.61/539,868, filed on Sep. 27, 2011, U.S. Provisional Application No.61/541,923, filed on Sep. 30, 2011, U.S. Provisional Application No.61/609,128, filed on Mar. 9, 2012, and U.S. Provisional Application No.61/636,524, filed on Apr. 20, 2012, the disclosures of which areincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The invention relates generally to structures incorporating additives.More particularly, the invention relates to patterned transparentconductors incorporating additives to impart improved functionality suchas electrical conductivity and low visibility patterning.

BACKGROUND

A transparent conductor permits the transmission of light whileproviding a conductive path for an electric current to flow through adevice including the transparent conductor. Traditionally, a transparentconductor is formed as a coating of a doped metal oxide, such astin-doped indium oxide (or ITO), which is disposed on top of a glass orplastic substrate. ITO coatings are typically formed through the use ofa dry process, such as through the use of specialized physical vapordeposition (e.g., sputtering) or specialized chemical vapor depositiontechniques. The resulting coating can exhibit good electricalconductivity. However, drawbacks to techniques for forming ITO coatingsinclude high cost, high process complexity, intensive energyrequirements, high capital expenditures for equipment, and poorproductivity.

For some applications, patterning of a transparent conductor isdesirable to form conductive traces and non-conductive gaps between thetraces. In the case of ITO coatings, patterning is typicallyaccomplished via photolithography. However, removing material viaphotolithography and related masking and etching processes furtherexacerbate the process complexity, the energy requirements, the capitalexpenditures, and the poor productivity for forming ITO-basedtransparent conductors. Also, low visibility of patterned transparentconductors is desirable for certain applications, such as touch screens.Conventional patterning techniques for ITO coatings typically result inpatterns that are visible to the eye, which can be undesirable for thoseapplications.

It is against this background that a need arose to develop thetransparent conductors and related manufacturing methods describedherein.

SUMMARY

One aspect of the invention relates to a patterned transparentconductor. In one embodiment, the patterned transparent conductorincludes a substrate and additives at least partially embedded into atleast one surface of the substrate and localized adjacent to the surfaceaccording to a pattern to form higher sheet conductance portions. Thehigher sheet conductance portions are laterally adjacent to lower sheetconductance portions.

In another embodiment, the patterned transparent conductor includes asubstrate, a coating disposed over at least one side of the substrate,and additives embedded into a surface of the coating according to apattern to form higher sheet conductance portions, wherein the additivesare localized within a depth from the surface that is less than athickness of the coating, and the higher sheet conductance portions arespaced apart by gaps that correspond to lower sheet conductanceportions.

In another embodiment, the patterned transparent conductor includes asubstrate, a patterned layer covering an area of the substrate, andadditives embedded into a surface of the patterned layer to form ahigher sheet conductance portion. The additives are localized within adepth from the surface that is less than a thickness of the patternedlayer, and a laterally adjacent area of the substrate corresponds to alower sheet conductance portion.

Other aspects and embodiments of the invention are also contemplated.The foregoing summary and the following detailed description are notmeant to restrict the invention to any particular embodiment but aremerely meant to describe some embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the nature and objects of some embodimentsof the invention, reference should be made to the following detaileddescription taken in conjunction with the accompanying drawings.

FIG. 1A and FIG. 1B illustrate transparent conductors implemented inaccordance with embodiments of the invention.

FIG. 2A through FIG. 2C illustrate manufacturing methods to formtransparent conductors, according to embodiments of the invention.

FIG. 3A through FIG. 3B illustrate a manufacturing method of a patternedtransparent conductor, according to an embodiment of the invention.

FIG. 4 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 5 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 6 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 7 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 8 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 9 illustrates a cross section of a patterned transparent conductorincluding additives that are embedded to varying depths into anembedding surface S of a host material, according to an embodiment ofthe invention.

FIG. 10 through FIG. 12 illustrate roll-to-roll techniques that usecorona treatment, according to embodiments of the invention.

FIG. 13 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 14 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 15 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 16 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 17 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 18 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 19 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 20 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 21 illustrates a manufacturing method of a patterned transparentconductor, according to an embodiment of the invention.

FIG. 22A through FIG. 22C illustrate various options of a generalizedmanufacturing method of a patterned transparent conductor, according toembodiments of the invention.

FIG. 23A through FIG. 23F illustrate examples of patterned transparentconductors formed according to the method of FIG. 22A through FIG. 22C,according to embodiments of the invention.

FIG. 24 illustrates a touch screen device according to an embodiment ofthe invention.

FIG. 25A and FIG. 25B include microscope images illustrating a patternedtransparent conductor, according to embodiments of the invention.

DETAILED DESCRIPTION Definitions

The following definitions apply to some of the aspects described withregard to some embodiments of the invention. These definitions maylikewise be expanded upon herein.

As used herein, the singular terms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. Thus, forexample, reference to an object can include multiple objects unless thecontext clearly dictates otherwise.

As used herein, the term “set” refers to a collection of one or moreobjects. Thus, for example, a set of objects can include a single objector multiple objects. Objects of a set can also be referred to as membersof the set. Objects of a set can be the same or different. In someinstances, objects of a set can share one or more commoncharacteristics.

As used herein, the term “adjacent” refers to being near or adjoining.Adjacent objects can be spaced apart from one another or can be inactual or direct contact with one another. In some instances, adjacentobjects can be connected to one another or can be formed integrally withone another.

As used herein, the terms “connect,” “connected,” and “connection” referto an operational coupling or linking. Connected objects can be directlycoupled to one another or can be indirectly coupled to one another, suchas via another set of objects.

As used herein, the terms “substantially” and “substantial” refer to aconsiderable degree or extent. When used in conjunction with an event orcircumstance, the terms can refer to instances in which the event orcircumstance occurs precisely as well as instances in which the event orcircumstance occurs to a close approximation, such as accounting fortypical tolerance levels of the manufacturing methods described herein.

As used herein, the terms “optional” and “optionally” mean that thesubsequently described event or circumstance may or may not occur andthat the description includes instances where the event or circumstanceoccurs and instances in which it does not.

As used herein, relative terms, such as “inner,” “interior,” “outer,”“exterior,” “top,” “bottom,” “front,” “rear,” “back,” “upper,”“upwardly,” “lower,” “downwardly,” “vertical,” “vertically,” “lateral,”“laterally,” “above,” and “below,” refer to an orientation of a set ofobjects with respect to one another, such as in accordance with thedrawings, but do not require a particular orientation of those objectsduring manufacturing or use.

As used herein, the term “nanometer range” or “nm range” refers to arange of dimensions from about 1 nanometer (“nm”) to about 1 micrometer(“μm”). The nm range includes the “lower nm range,” which refers to arange of dimensions from about 1 nm to about 10 nm, the “middle nmrange,” which refers to a range of dimensions from about 10 nm to about100 nm, and the “upper nm range,” which refers to a range of dimensionsfrom about 100 nm to about 1 μm.

As used herein, the term “micrometer range” or “μm range” refers to arange of dimensions from about 1 μm to about 1 millimeter (“mm”). The μmrange includes the “lower μm range,” which refers to a range ofdimensions from about 1 μm to about 10 μm, the “middle μm range,” whichrefers to a range of dimensions from about 10 μm to about 100 μm, andthe “upper μm range,” which refers to a range of dimensions from about100 μm to about 1 mm.

As used herein, the term “aspect ratio” refers to a ratio of a largestdimension or extent of an object and an average of remaining dimensionsor extents of the object, where the remaining dimensions are orthogonalwith respect to one another and with respect to the largest dimension.In some instances, remaining dimensions of an object can besubstantially the same, and an average of the remaining dimensions cansubstantially correspond to either of the remaining dimensions. Forexample, an aspect ratio of a cylinder refers to a ratio of a length ofthe cylinder and a cross-sectional diameter of the cylinder. As anotherexample, an aspect ratio of a spheroid refers to a ratio of a major axisof the spheroid and a minor axis of the spheroid.

As used herein, the term “nano-sized” object refers to an object thathas at least one dimension in the nm range. A nano-sized object can haveany of a wide variety of shapes, and can be formed of a wide variety ofmaterials. Examples of nano-sized objects include nanowires, nanotubes,nanoplatelets, nanoparticles, and other nanostructures.

As used herein, the term “nanowire” refers to an elongated, nano-sizedobject that is substantially solid. Typically, a nanowire has a lateraldimension (e.g., a cross-sectional dimension in the form of a width, adiameter, or a width or diameter that represents an average acrossorthogonal directions) in the nm range, a longitudinal dimension (e.g.,a length) in the μm range, and an aspect ratio that is about 3 orgreater.

As used herein, the term “nanoplatelet” refers to a planar-like,nano-sized object that is substantially solid.

As used herein, the term “nanotube” refers to an elongated, hollow,nano-sized object. Typically, a nanotube has a lateral dimension (e.g.,a cross-sectional dimension in the form of a width, an outer diameter,or a width or outer diameter that represents an average acrossorthogonal directions) in the nm range, a longitudinal dimension (e.g.,a length) in the μm range, and an aspect ratio that is about 3 orgreater.

As used herein, the term “nanoparticle” refers to a spheroidal (e.g.,approximately spheroidal), nano-sized object. Typically, each dimension(e.g., a cross-sectional dimension in the form of a width, a diameter,or a width or diameter that represents an average across orthogonaldirections) of a nanoparticle is in the nm range, and the nanoparticlehas an aspect ratio that is less than about 3, such as about 1.

As used herein, the term “micron-sized” object refers to an object thathas at least one dimension in the μm range. Typically, each dimension ofa micron-sized object is in the μm range or beyond the μm range. Amicron-sized object can have any of a wide variety of shapes, and can beformed of a wide variety of materials. Examples of micron-sized objectsinclude microwires, microtubes, microparticles, and othermicrostructures.

As used herein, the term “microwire” refers to an elongated,micron-sized object that is substantially solid. Typically, a microwirehas a lateral dimension (e.g., a cross-sectional dimension in the formof a width, a diameter, or a width or diameter that represents anaverage across orthogonal directions) in the μm range and an aspectratio that is about 3 or greater.

As used herein, the term “microtube” refers to an elongated, hollow,micron-sized object. Typically, a microtube has a lateral dimension(e.g., a cross-sectional dimension in the form of a width, an outerdiameter, or a width or outer diameter that represents an average acrossorthogonal directions) in the μm range and an aspect ratio that is about3 or greater.

As used herein, the term “microparticle” refers to a spheroidal,micron-sized object. Typically, each dimension (e.g., a cross-sectionaldimension in the form of a width, a diameter, or a width or diameterthat represents an average across orthogonal directions) of amicroparticle is in the μm range, and the microparticle has an aspectratio that is less than about 3, such as about 1.

Transparent Conductors

Embodiments of the invention relate to electrically conductive orsemiconducting additives that are incorporated into host materials foruse as transparent conductors or other types of conductive structures.Embodiments of transparent conductors exhibit improved performance(e.g., higher electrical and thermal conductivity and higher lighttransmittance), as well as cost benefits arising from their structure,composition, and manufacturing process. In some embodiments, transparentconductors can be manufactured by a surface embedding process in whichadditives are physically embedded into a host material, while preservingdesired characteristics of the host material (e.g., transparency) andimparting additional desired characteristics to the resultingtransparent conductors (e.g., electrical conductivity). In someembodiments, transparent conductors can be patterned so as to include afirst set of portions having a first sheet conductance and a second setof portions having a second sheet conductance lower than the first sheetconductance. The first set of portions can correspond to higher sheetconductance portions that function as conductive traces or grids, whilethe second set of portions can correspond to lower sheet conductanceportions that function as gaps for electrically isolating the conductivetraces. Additives can be surface-embedded into either, or both, of theportions.

FIG. 1A and FIG. 1B illustrate examples of transparent conductors 120and 126 implemented in accordance with embodiments of the invention.Specifically, FIG. 1A is a schematic of surface-embedded additives 130that form a network that is partially exposed and partially buried intoa top, embedding surface 134 of a host material 132, which correspondsto a substrate. The embedding surface 134 also can be a bottom surfaceof the host material 132, or multiple surfaces (e.g., both top andbottom surfaces) on different sides of the host material 132 can beembedded with the same or different additives. As illustrated in FIG.1A, the network of the additives 130 is localized adjacent to theembedding surface 134 and within an embedded region 138 of the hostmaterial 132, with a remainder of the host material 132 largely devoidof the additives 130. In the illustrated embodiment, the embedded region138 is relatively thin (e.g., having a thickness less than or much lessthan an overall thickness of the host material 132, or having athickness comparable to a characteristic dimension of the additives130), and, therefore, can be referred to as “planar” or “planar-like.”The transparent conductor 120 can be patterned, such that FIG. 1A canrepresent a view of a particular portion of the patterned transparentconductor 120, such as a higher sheet conductance portion. FIG. 1A alsocan represent a view of a lower sheet conductance portion, in which thenetwork of the additives 130 is treated or otherwise processed to resultin reduced electrical conductivity.

FIG. 1B is a schematic of surface-embedded additives 154 that form anetwork that is partially exposed and partially buried into a top,embedding surface 156 of a host material 158, which corresponds to acoating or other secondary material that is disposed on top of asubstrate 160. As illustrated in FIG. 1B, the network of the additives154 can be localized adjacent to the embedding surface 156 and within anembedded region 162 of the host material 158, with a remainder of thehost material 158 largely devoid of the additives 154. It is alsocontemplated that the additives 154 can be distributed throughout alarger volume fraction within the host material 158, such as in the caseof a relatively thin coating having a thickness comparable to acharacteristic dimension of the additives 154. In the illustratedembodiment, the embedded region 162 is relatively thin, and, therefore,can be referred to as “planar” or “planar-like.” The transparentconductor 126 can be patterned, such that FIG. 1B can represent a viewof a particular portion of the patterned transparent conductor 126, suchas a higher sheet conductance portion. FIG. 1B also can represent a viewof a lower sheet conductance portion, in which the network of theadditives 154 is treated or otherwise processed to result in reducedelectrical conductivity.

One aspect of certain transparent conductors described herein is theprovision of a vertical additive concentration gradient or profilewithin at least a portion of a host material, namely a gradient orprofile along a thickness direction of the host material. Bulkincorporation within a substrate or a coating aims to provide arelatively uniform vertical additive concentration profile throughoutthe substrate or the coating. In contrast, certain transparentconductors described herein allow for variable, controllable verticaladditive concentration profile, in accordance with a localization ofadditives within an embedded region of at least a portion of a hostmaterial. For certain implementations, the extent of localization ofadditives within an embedded region is such that at least a majority (byweight, volume, or number density) of the additives are included withinthe embedded region, such as at least about 60% (by weight, volume, ornumber density) of the additives are so included, at least about 70% (byweight, volume, or number density) of the additives are so included, atleast about 80% (by weight, volume, or number density) of the additivesare so included, at least about 90% (by weight, volume, or numberdensity) of the additives are so included, or at least about 95% (byweight, volume, or number density) of the additives are so included. Forexample, substantially all of the additives can be localized within theembedded region, such that a remainder of the host material issubstantially devoid of the additives. In the case of a patternedtransparent conductor, localization of additives can vary according to ahorizontal additive concentration gradient or profile in a hostmaterial, or can vary across multiple host materials included in thepatterned transparent conductor.

Additives can be in the form of nano-sized additives, micron-sizedadditives, or a combination thereof. To impart electrical conductivity,additives can include an electrically conductive material, asemiconductor, or a combination thereof.

Examples of electrically conductive materials include metals (e.g.,silver, copper, and gold in the form of silver nanowires, coppernanowires, and gold nanowires), metal alloys, silver-nickel, silveroxide, silver with a polymeric capping agent, silver-copper,copper-nickel, carbon-based conductors (e.g., in the form of carbonnanotubes, graphene, and buckyballs), conductive ceramics (e.g.,conducting oxides and chalcogenides that are optionally doped andtransparent, such as metal oxides and chalcogenides that are optionallydoped and transparent), electrically conductive polymers (e.g.,polyaniline, poly(acetylene), poly(pyrrole), poly(thiophene),poly(p-phenylene sulfide), poly(p-phenylene vinylene) (or PPV),poly(3-alkylthiophene), olyindole, polypyrene, polycarbazole,polyazulene, polyazepine, poly(fluorene), polynaphthalene, melanins,poly(3,4-ethylenedioxythiophene) (or PEDOT), poly(styrenesulfonate) (orPSS), PEDOT-PSS, PEDOT-polymethacrylic acid (or PEDOT-PMA),poly(3-hexylthiophene) (or P3HT), poly(3-octylthiophene) (or P3OT),poly(C-61-butyric acid-methyl ester) (or PCBM), andpoly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene](orMEH-PPV)), and any combination thereof.

Examples of semiconductor materials include semiconducting polymers,Group IVB elements (e.g., carbon (or C), silicon (or Si), and germanium(or Ge)), Group IVB-IVB binary alloys (e.g., silicon carbide (or SiC)and silicon germanium (or SiGe)), Group IIB-VIB binary alloys (e.g.,cadmium selenide (or CdSe), cadmium sulfide (or CdS), cadmum telluride(or CdTe), zinc oxide (or ZnO), zinc selenide (or ZnSe), zinc telluride(or ZnTe), and zinc sulfide (or ZnS)), Group IIB-VIB ternary alloys(e.g., cadmium zinc telluride (or CdZnTe), mercury cadmium telluride (orHgCdTe), mercury zinc telluride (or HgZnTe), and mercury zinc selenide(or HgZnSe)), Group IIIB-VB binary alloys (e.g., aluminum antimonide (orAlSb), aluminum arsenide (or AlAs), aluminium nitride (or AlN),aluminium phosphide (or AlP), boron nitride (or BN), boron phosphide (orBP), boron arsenide (or BAs), gallium antimonide (or GaSb), galliumarsenide (or GaAs), gallium nitride (or GaN), gallium phosphide (orGaP), indium antimonide (or InSb), indium arsenide (or InAs), indiumnitride (or InN), and indium phosphide (or InP)), Group IIIB-VB ternaryalloys (e.g., aluminium gallium arsenide (or AlGaAs or Al_(x)Ga_(1-x)As), indium gallium arsenide (or InGaAs or In_(x)Ga_(1-x)As),indium gallium phosphide (or InGaP), aluminium indium arsenide (orAlInAs), aluminium indium antimonide (or AllnSb), gallium arsenidenitride (or GaAsN), gallium arsenide phosphide (or GaAsP), aluminiumgallium nitride (or AlGaN), aluminium gallium phosphide (or AlGaP),indium gallium nitride (or InGaN), indium arsenide antimonide (orInAsSb), and indium gallium antimonide (or InGaSb)), Group IIIB-VBquaternary alloys (e.g., aluminium gallium indium phosphide (orAlGaInP), aluminium gallium arsenide phosphide (or AlGaAsP), indiumgallium arsenide phosphide (or InGaAsP), aluminium indium arsenidephosphide (or AlInAsP), aluminium gallium arsenide nitride (or AlGaAsN),indium gallium arsenide nitride (or InGaAsN), indium aluminium arsenidenitride (or InAlAsN), and gallium arsenide antimonide nitride (orGaAsSbN)), and Group IIIB-VB quinary alloys (e.g., gallium indiumnitride arsenide antimonide (or GaInNAsSb) and gallium indium arsenideantimonide phosphide (or GaInAsSbP)), Group IB-VIIB binary alloys (e.g.,cupruous chloride (or CuCl)), Group IVB-VIB binary alloys (e.g., leadselenide (or PbSe), lead sulfide (or PbS), lead telluride (or PbTe), tinsulfide (or SnS), and tin telluride (or SnTe)), Group IVB-VIB ternaryalloys (e.g., lead tin telluride (or PbSnTe), thallium tin telluride (orTl₂SnTes), and thallium germanium telluride (or Tl₂GeTes)), Group VB-VIBbinary alloys (e.g., bismuth telluride (or Bi₂Te₃)), Group IIB-VB binaryalloys (e.g., cadmium phosphide (or Cd₃P₂), cadmium arsenide (orCd₃As₂), cadmium antimonide (or Cd₃Sb₂), zinc phosphide (or Zn₃P₂), zincarsenide (or Zn₃As₂), and zinc antimonide (or Zn₃Sb₂)), and otherbinary, ternary, quaternary, or higher order alloys of Group IB (orGroup 11) elements, Group IIB (or Group 12) elements, Group IIIB (orGroup 13) elements, Group IVB (or Group 14) elements, Group VB (or Group15) elements, Group VIB (or Group 16) elements, and Group VIIB (or Group17) elements, such as copper indium gallium selenide (or CIGS), as wellas any combination thereof.

Additives can include, for example, metallic or semiconductingnanoparticles, nanowires (e.g. silver, copper, or zinc), nanoplates,nanoflakes, nanofibers, nanorods, nanotubes (e.g., carbon nanotubes,multi-walled nanotubes (“MWNTs”), single-walled nanotubes (“SWNTs”),double-walled nanotubes (“DWNTs”), and graphitized or modifiednanotubes), fullerenes, buckyballs, graphene, microparticles,microwires, microtubes, core-shell nanoparticles or microparticles,core-multishell nanoparticles or microparticles, core-shell nanowires,and other additives having shapes that are substantially tubular, cubic,spherical, or pyramidal, and characterized as amorphous, crystalline,tetragonal, hexagonal, trigonal, orthorhombic, monoclinic, or triclinic,or any combination thereof.

Examples of core-shell nanoparticles and core-shell nanowires includethose with a ferromagnetic core (e.g., iron, cobalt, nickel, manganese,as well as their oxides and alloys formed with one or more of theseelements), with a shell formed of a metal, a metal alloy, a metal oxide,carbon, or any combination thereof (e.g., silver, copper, gold,platinum, a conducting oxide or chalcogenide, graphene, and othermaterials listed as suitable additives herein). A particular example ofa core-shell nanowire is one with a silver core and a gold shell (or aplatinum shell or another type of shell) surrounding the silver core toreduce or prevent oxidation of the silver core. Another example of acore-shell nanowire is one with a silver core (or a core formed ofanother metal or other electrically conductive material), with a shellor other coating formed of one or more of the following: (a) conductingpolymers, such as poly(3,4-ethylenedioxythiophene) (or PEDOT) andpolyaniline (or PANI); (b) conducting oxides, chalcogenides, andceramics (e.g., deposited by sol-gel, chemical vapor deposition,physical vapor deposition, plasma-enhanced chemical vapor deposition, orchemical bath deposition); (c) insulators in the form of ultra-thinlayers, such as polymers, SiO₂, BaTiO, and TiO₂; and (d) thin layers ofmetals, such as gold, copper, nickel, chromium, molybdenum, andtungsten. Such coated or core-shell form of nanowires can be desirableto impart electrical conductivity, while avoiding or reducing adverseinteractions with a host material, such as potential yellowing or otherdiscoloration in the presence of a metal such as silver, oxidation(e.g., a silver/gold core/shell nanowires can have substantially loweroxidation due to the gold shell), and sulfidation (e.g., asilver/platinum core/shell nanowire can have substantially lowersulfidation due to the platinum shell).

For certain implementations, high aspect ratio additives are desirable,such as in the form of nanowires, nanotubes, and combinations thereof.For example, desirable additives include nanotubes formed of carbon orother materials (e.g., MWNTs, SWNTs, graphitized MWNTs, graphitizedSWNTs, modified MWNTs, modified SWNTs, and polymer-containingnanotubes), nanowires formed of a metal, a metal oxide, a metal alloy,or other materials (e.g., silver nanowires, copper nanowires, zinc oxidenanowires (undoped or doped by, for example, aluminum, boron, fluorine,and others), tin oxide nanowires (undoped or doped by, for example,fluorine), cadmium tin oxide nanowires, tin-doped indium oxide (or ITO)nanowires, polymer-containing nanowires, and gold nanowires), as well asother materials that are electrically conductive or semiconducting andhaving a variety of shapes, whether cylindrical, spherical, pyramidal,or otherwise. Additional examples of additives include those formed ofactivated carbon, graphene, carbon black, ketjen black, andnanoparticles formed of a metal, a metal oxide, a metal alloy, or othermaterials (e.g., silver nanoparticles, copper nanoparticles, zinc oxidenanoparticles, ITO nanoparticles, and gold nanoparticles).

A host material can have a variety of shapes and sizes, can betransparent, translucent, or opaque, can be flexible, bendable,foldable, stretchable, or rigid, can be electromagnetically opaque orelectromagnetically transparent, and can be electrically conductive,semiconducting, or insulating. A host material can be in the form of alayer, a film, or a sheet serving as a substrate, or can be in the formof a coating or multiple coatings disposed on top of a substrate oranother material. A host material can be patterned or unpatterned. Forexample, a host material can be formed as a patterned layer that coverscertain areas of an underlying substrate while leaving remaining areasof the substrate exposed. As another example, a first host material canbe formed as a first patterned layer overlying certain areas of anunderlying substrate, and a second host material (which can differ fromthe first host material in some manner) can be formed as a secondpatterned layer that covers remaining areas of the substrate. In suchmanner, the first host material can provide a first pattern, and thesecond host material can provide a second pattern that is an “inverse”of the first pattern. Stated in another way, the first host material canprovide “positive” portions of a pattern, and the second host materialcan provide “negative” portions of the pattern.

Examples of suitable host materials include organic materials, inorganicmaterials, and hybrid organic-inorganic materials. For example, a hostmaterial can include a thermoplastic polymer, a thermoset polymer, anelastomer, or a copolymer or other combination thereof, such as selectedfrom polyolefin, polyethylene (or PE), polypropylene (or PP), ethylenevinyl acetate (or EVA), an ionomer, polyvinyl butyral (or PVB),polyacrylate, polyester, polysulphone, polyamide, polyimide,polyurethane, polyvinyl, fluoropolymer, polycarbonate (or PC),polysulfone, polylactic acid, polymer based on allyl diglycol carbonate,nitrile-based polymer, acrylonitrile butadiene styrene (or ABS), cyclicolefin polymer (or COP) (e.g., available under the trademark ARTON® andZeonorFilm®), cyclic olefin resin, cellulose triacetate (or TAC),phenoxy-based polymer, phenylene ether/oxide, a plastisol, an organosol,a plastarch material, a polyacetal, aromatic polyamide, polyamide-imide,polyarylether, polyetherimide, polyarylsulfone, polybutylene,polyketone, polymethylpentene, polyphenylene, polystyrene, high impactpolystyrene, polymer based on styrene maleic anhydride, polymer based onpolyallyl diglycol carbonate monomer, bismaleimide-based polymer,polyallyl phthalate, thermoplastic polyurethane, high densitypolyethylene, low density polyethylene, copolyesters (e.g., availableunder the trademark Tritan™), polyvinyl chloride (or PVC), acrylic-basedpolymer, polyethylene terephthalate glycol (or PETG), polyethyleneterephthalate (or PET), epoxy, epoxy-containing resin, melamine-basedpolymer, silicone and other silicon-containing polymers (e.g.,polysilanes and polysilsesquioxanes), polymers based on acetates,poly(propylene fumarate), poly(vinylidene fluoride-trifluoroethylene),poly-3-hydroxybutyrate polyesters, polyamide, polycaprolactone,polyglycolic acid (or PGA), polyglycolide, polylactic acid (or PLA),polylactide acid plastics, polyphenylene vinylene, electricallyconducting polymer (e.g., polyaniline, poly(acetylene), poly(pyrrole),poly(thiophene), poly(p-phenylene sulfide), poly(p-phenylene vinylene)(or PPV), poly(3-alkylthiophene), olyindole, polypyrene, polycarbazole,polyazulene, polyazepine, poly(fluorene), polynaphthalene, melanins,poly(3,4-ethylenedioxythiophene) (or PEDOT), poly(styrenesulfonate) (orPSS), PEDOT-PSS, PEDOT-polymethacrylic acid (or PEDOT-PMA),poly(3-hexylthiophene) (or P3HT), poly(3-octylthiophene) (or P3OT),poly(C-61-butyric acid-methyl ester) (or PCBM), andpoly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene](orMEH-PPV)), polyolefins, liquid crystal polymers, polyurethane,polyester, copolyester, polymethyl mechacrylate copolymer,tetrafluoroethylene-based polymer, sulfonated tetrafluoroethylenecopolymer, ionomers, fluorinated ionomers, polymer corresponding to, orincluded in, polymer electrolyte membranes, ethanesulfonylfluoride-based polymer, polymer based on2-[1-[difluoro-[(trifluoroethenyl)oxy]methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2,-tetrafluoro-(with tetrafluoro ethylene,tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octenesulfonic acidcopolymer), polypropylene, polybutene, polyisobutene, polyisoprene,polystyrene, polylactic acid, polyglycolide, polyglycolic acid,polycaprolactone, polymer based on vinylidene fluoride, polymer based ontrifluoroethylene, poly(vinylidene fluoride-trifluoroethylene),polyphenylene vinylene, polymer based on copper phthalocyanine,graphene, poly(propylene fumarate), cellophane, cuprammonium-basedpolymer, rayon, and biopolymers (e.g., cellulose acetate (or CA),cellulose acetate butyrate (or CAB), cellulose acetate propionate (orCAP), cellulose propionate (or CP), polymers based on urea, wood,collagen, keratin, elastin, nitrocellulose, plastarch, celluloid,bamboo, bio-derived polyethylene, carbodiimide, cartilage, cellulosenitrate, cellulose, chitin, chitosan, connective tissue, copperphthalocyanine, cotton cellulose, elastin, glycosaminoglycans, linen,hyaluronic acid, nitrocellulose, paper, parchment, plastarch, starch,starch-based plastics, vinylidene fluoride, and viscose), polymers basedon cyclic olefins (e.g., cyclic olefin polymers and copolymers), or anymonomer, copolymer, blend, or other combination thereof. Additionalexamples of suitable host materials include ceramics, such as dielectricor non-conductive ceramics (e.g., SiO₂-based glass; SiO_(x)-based glass;TiO_(x)-based glass; other titanium, cerium, magnesium analogues ofSiO_(x)-based glass; spin-on glass; glass formed from sol-gelprocessing, silane precursor, siloxane precursor, silicate precursor,tetraethyl orthosilicate, silane, siloxane, phosphosilicates, spin-onglass, silicates, sodium silicate, potassium silicate, a glassprecursor, a ceramic precursor, silsesquioxane, metallasilsesquioxanes,polyhedral oligomeric silsesquioxanes, halosilane, sol-gel,silicon-oxygen hydrides, silicones, stannoxanes, silathianes, silazanes,polysilazanes, metallocene, titanocene dichloride, vanadocenedichloride; and other types of glasses), conductive ceramics (e.g.,conducting oxides and chalcogenides that are optionally doped andtransparent, such as metal oxides and chalcogenides that are optionallydoped and transparent), and any combination thereof. Additional examplesof suitable host materials include electrically conductive materials andsemiconductors listed above as suitable materials for additives. Thehost material can be, for example, n-doped, p-doped, or un-doped.Further examples of suitable host materials include polymer-ceramiccomposite, polymer-wood composite, polymer-carbon composite (e.g.,formed of ketjen black, activated carbon, carbon black, graphene, andother forms of carbon), polymer-metal composite, polymer-oxide, or anycombination thereof.

In some embodiments, confining additives to a “planar” or “planar-like”embedded region within at least a portion of a host material can lead todecreased topological disorder of the additives and increased occurrenceof junction formation between the additives for improved electricalconductivity. Although an embedded region is sometimes referred as“planar,” it will be understood that such embedded region is typicallynot strictly two-dimensional, as the additives themselves are typicallythree-dimensional. Rather, “planar” can be used in a relative sense,with a relatively thin, slab-like (or layered) local concentration ofthe additives within a certain region of the host material, and with theadditives largely absent from a remainder of the host material. It isnoted that the local concentration of additives can be non-planar in thesense that it can be non-flat. For example, the additives can beconcentrated in a thin region of the host material that is characterizedby curvature with respect to one or more axes, with the additiveslargely absent from a remainder of the host material. It will also beunderstood that an embedded region can be referred as “planar,” eventhough such an embedded region can have a thickness that is greater than(e.g., several times greater than) a characteristic dimension ofadditives. In general, an embedded region can be located adjacent to aside of a host material, adjacent to a middle of the host material, oradjacent to any arbitrary location along a thickness direction of thehost material, and multiple embedded regions can be located adjacent toone another or spaced apart from one another within the host material.Each embedded region can include one or more types of additives, andembedded regions (which are located in the same host material) caninclude different types of additives. In the case of a patternedtransparent conductor, multiple embedded regions can be located across ahost material according to a pattern to define a set of higher sheetconductance portions, a set of lower sheet conductance portions, orboth. In some embodiments, by confining electrically conductiveadditives to a set of “planar” embedded regions of a host material (asopposed to randomly throughout the host material), a higher electricalconductivity can be achieved for a given amount of the additives perunit of area. Any additives not confined to an embedded region representan excess amount of additives that can be omitted.

In some embodiments, transparent conductors can have additives embeddedor otherwise incorporated into at least a portion of a host materialfrom about 10% (or less, such as from about 0.1%) by volume into anembedding surface and up to about 100% by volume into the embeddingsurface, and can have the additives exposed at varying surface areacoverage, such as from about 0.1% surface area coverage (or less, suchas 0% when an embedded region is entirely below the surface, or when theadditives are completely encapsulated by the host material) up to about99.9% (or more) surface area coverage. For example, in terms of a volumeof an additive embedded below the embedding surface relative to a totalvolume of the additive, at least one additive can have an embeddedvolume percentage (or a population of the additives can have an averageembedded volume percentage) in the range of about 0% to about 100%, suchas from 10% to about 50%, or from about 50% to about 100%.

Transparent conductors of some embodiments can have an embedded regionwith a thickness greater than a characteristic dimension of additivesused (e.g., for nanowires, greater than a diameter of an individualnanowire or an average diameter across the nanowires), with theadditives largely confined to the embedded region with the thicknessless than an overall thickness of the host material. For example, thethickness of the embedded region can be no greater than about 95% of theoverall thickness of the host material, such as no greater than about80%, no greater than about 75%, no greater than about 50%, no greaterthan about 40%, no greater than about 30%, no greater than about 20%, nogreater than about 10%, or no greater than about 5% of the overallthickness.

In some embodiments, additives can be embedded or otherwise incorporatedinto at least a portion of a host material by varying degrees relativeto a characteristic dimension of the additives used (e.g., fornanowires, relative to a diameter of an individual nanowire or anaverage diameter across the nanowires). For example, in terms of adistance of a furthest embedded point on an additive below an embeddingsurface, at least one additive can be embedded to an extent of more thanabout 100% of the characteristic dimension, or can be embedded to anextent of not more than about 100% of the characteristic dimension, suchas at least about 5% or about 10% and up to about 80%, up to about 50%,or up to about 25% of the characteristic dimension. As another example,a population of the additives, on average, can be embedded to an extentof more than about 100% of the characteristic dimension, or can beembedded to an extent of not more than about 100% of the characteristicdimension, such as at least about 5% or about 10% and up to about 80%,up to about 50%, or up to about 25% of the characteristic dimension. Aswill be understood, the extent to which additives are embedded into ahost material can impact a roughness of an embedding surface, such aswhen measured as an extent of variation of heights across the embeddingsurface (e.g., a standard deviation relative to an average height). Insome embodiments, a roughness of the surface-embedded structure is lessthan a characteristic dimension of partially embedded additives.

In some embodiments, at least one additive can extend out from anembedding surface of a host material from about 0.1 nm to about 1 cm,such as from about 1 nm to about 50 nm, from about 50 nm to 100 nm, orfrom about 100 nm to about 100 microns. In other embodiments, apopulation of additives, on average, can extend out from an embeddingsurface of a host material from about 0.1 nm to about 1 cm, such as fromabout 1 nm to about 50 nm, from about 50 nm to 100 nm, or from about 100nm to about 100 microns. In other embodiments, substantially all of asurface area of a host material (e.g., an area of an embedding surface)is occupied by additives. In other embodiments, up to about 100% or upto about 75% of the surface area is occupied by additives, such as up toabout 50% of the surface area, up to about 25% of the surface area, upto about 10%, up to about 5%, up to about than 3% of the surface area,or up to about 1% of the surface area is occupied by additives.Additives need not extend out from an embedding surface of a hostmaterial, and can be localized entirely below the embedding surface Thedegree of embedding and surface coverage of additives for asurface-embedded structure can be selected in accordance with aparticular application.

In some embodiments, if nanowires are used as additives, characteristicsthat can influence electrical conductivity and other desirablecharacteristics include, for example, nanowire concentration, density,or loading level; surface area coverage; nanowire length; nanowirediameter; uniformity of the nanowires; material type; stability of thenanowire formulations; wire-wire junction resistance; host-materialresistance; nanowire conductivity; crystallinity of the nanowire; andpurity. There can be a preference for nanowires with a low junctionresistance and a low bulk resistance in some embodiments. For attaininghigher electrical conductivity while maintaining high transparency,thinner diameter, longer length nanowires can be used (e.g., withrelatively large aspect ratios to facilitate nanowire junction formationand in the range of about 50 to about 2,000, such as from about 50 toabout 1,000, or from about 100 to about 800), and metallic nanowires,such as silver, copper, and gold nanowires, can be used. In otherembodiments, if the nanowires are thin, their bulk conductivity candecrease because of the small cross-sectional area of the wires;therefore, in some embodiments, thicker diameter wires can be selected.Using nanowires as additives to form nanowire networks, such as silvernanowire networks, can be desirable for some embodiments. Other metallicnanowires, non-metallic nanowires, such as ITO and other oxide andchalcogenide nanowires, also can be used. Additives composed ofsemiconductors with bandgaps outside the visible optical spectrumenergies (e.g., <1.8 eV and >3.1 eV) or approximately near this range,can be used to create transparent conductors with high opticaltransparency in that visible light will typically not be absorbed by thebandgap energies or by interfacial traps therein. Various dopants can beused to tune the conductivity of these aforementioned semiconductors,taking into account the shifted Fermi levels and bandgap edges via theMoss-Burstein effect. The nanowires can be largely uniform ormonodisperse in terms of dimensions (e.g., diameter and length), such asthe same within about 5% (e.g., a standard deviation relative to anaverage diameter or length), the same within about 10%, the same withinabout 15%, or the same within about 20%. Purity can be, for example, atleast about 50%, at least about 75%, at least about 85%, at least about90%, at least about 95%, at least about 99%, at least about 99.9%, or atleast about 99.99%. Surface area coverage of nanowires can be, forexample, up to about 100%, less than about 100%, up to about 75%, up toabout 50%, up to about 25%, up to about 10%, up to about 5%, up to about3%, or up to about 1%. Silver nanowires can be particularly desirablefor certain embodiments, since silver oxide, which can form (or can beformed) on surfaces of the nanowires as a result of oxidation, iselectrically conductive. Also, core-shell nanowires (e.g., silver corewith gold or platinum shell) also can decrease junction resistance.Nanowires can be solution synthesized via a number of processes, such asa solution-phase synthesis (e.g., the polyol process), avapor-liquid-solid (“VLS”) synthesis, an electrospinning process (e.g.,using a polyvinyl-based polymer and silver nitrate, then annealing informing gas, and baking), a suspension process (e.g., chemical etchingor nano-melt retraction), and so forth.

In some embodiments, if nanotubes are used as additives (whether formedof carbon, a metal, a metal alloy, a metal oxide, or another material),characteristics that can influence electrical conductivity and otherdesirable characteristics include, for example, nanotube concentration,density, or loading level; surface area coverage; nanotube length;nanotube inner diameter; nanotube outer diameter; whether single-walledor multi-walled nanotubes are used; uniformity of the nanotubes;material type; and purity. There can be a preference for nanotubes witha low junction resistance in some embodiments. For reduced scattering inthe context of certain devices such as displays, nanotubes, such ascarbon nanotubes, can be used to form nanotube networks. Alternatively,or in combination, smaller diameter nanowires can be used to achieve asimilar reduction in scattering relative to the use of nanotubes.Nanotubes can be largely uniform or monodisperse in terms of dimensions(e.g., outer diameter, inner diameter, and length), such as the samewithin about 5% (e.g., a standard deviation relative to an averageouter/inner diameter or length), the same within about 10%, the samewithin about 15%, or the same within about 20%. Purity can be, forexample, at least about 50%, at least about 75%, at least about 85%, atleast about 90%, at least about 95%, at least about 99%, at least about99.9%, or at least about 99.99%. Surface area coverage of nanotubes canbe, for example, up to about 100%, less than about 100%, up to about75%, up to about 50%, up to about 25%, up to about 10%, up to about 5%,up to about 3%, or up to about 1%.

In some embodiments, a combination of different types of high aspectratio electrically conductive or semiconducting additives (e.g.,conductive nanowires, nanotubes, or both) can be embedded into at leasta portion of a host material, resulting in a transparent yet conductivestructure. Specifically, the combination can include a first populationof additives having a first set of morphological characteristics (e.g.,length (average, median, or mode), diameter (average, median, or mode),aspect ratio (average, median, or mode), or a combination thereof) andat least a second population of additives having a second set ofmorphological characteristics that differ in some manner from the firstset of morphological characteristics. Each population of additives canbe largely uniform or monodisperse in terms of its respective set ofmorphological characteristics, such as the same within about 5% (e.g., astandard deviation relative to an average diameter, length, or aspectratio), the same within about 10%, the same within about 15%, or thesame within about 20%. The resulting combination of additives can bebimodal or multimodal. For example, longer and larger diameter nanowirescan promote lower percolation thresholds, thereby achieving highertransparency with lower conductive material usage. On the other hand,shorter and smaller diameter nanowires can promote lower haze and highertransmission of light through a percolating network. However, smallerdiameter nanowires may have higher Ohmic resistance compared to largerdiameter nanowires of the same material. The use of a combination oflonger and larger diameter nanowires and shorter and smaller diameternanowires provides a practical tradeoff between various factors,including higher transparency (e.g., lower percolation threshold fromthe longer nanowires), a lower haze (e.g., lower scattering from thesmaller diameter nanowires), and higher conductivity (e.g., lowerresistance from the larger diameter nanowires) relative to the use ofeither population of nanowires alone. By way of analogy and notlimitation, the longer and larger diameter nanowires can act as largercurrent arteries, while the shorter and smaller diameter nanowires canact as smaller current capillaries.

It should be understood that the number of additive types can be variedfor a given device or application. For example, any, or a combination,of silver nanowires, copper nanowires, and gold nanowires can be usedalong with ITO nanoparticles to yield high optical transparency and highelectrical conductivity. Similar combinations include, for example, any,or a combination, of silver nanowires, copper nanowires, and goldnanowires along with any one or more of ITO nanowires, ZnO nanowires,ZnO nanoparticles, silver nanoparticles, gold nanoparticles, SWNTs,MWNTs, fullerene-based materials (e.g., carbon nanotubes andbuckyballs), and ITO nanoparticles. The use of ITO nanoparticles,nanowires, or layers of conductive oxides or ceramics (e.g., ITO,aluminum-doped zinc oxide, or other types of doped or undoped zincoxides) can provide additional functionality, such as by serving as abuffer layer to adjust a work function in the context of a transparentconductor for use in a solar device, a thin-film solar device, an OLEDdisplay type device, an OLED lighting type device, or similar device toprovide a conductive path for the flow of an electric current, in placeof, or in combination with, a conductive path provided by otheradditives.

In some embodiments, additives are initially provided as discreteobjects. Upon embedding or incorporation into at least a portion of ahost material, the host material can envelop or surround the additivessuch that the additives become aligned or otherwise arranged within a“planar” or “planar-like” embedded region. In some embodiments for thecase of additives such as nanowires, nanotubes, microwires, microtubes,or other additives with an aspect ratio greater than 1, the additivesbecome aligned such that their lengthwise or longitudinal axes arelargely confined to within a range of angles relative to a horizontalplane, or another plane corresponding, or parallel, to a plane of anembedding surface. For example, the additives can be elongated and canbe aligned such that their lengthwise or longest-dimension axes, onaverage, are confined to a range from about −45° to about +45° relativeto the horizontal plane, such as from about −35° to about +35°, fromabout −25° to about +25°, from about −15° to about +15°, from about −5°to about +5°, from about −1° to about +1°, from about −0.1° to about+0.1°, or from about −0.01° to about +0.01°. Stated in another way,lengthwise axes of the additives can be confined such that θ<SIN⁻¹(t/L), where L=length of an additive, t=thickness of the host material,and θ is an angle relative to a horizontal plane corresponding to theembedding surface. In this example, little or substantially none of theadditives can have their lengthwise or longitudinal axes orientedoutside of the range from about −45° to about +45° relative to thehorizontal plane. Within the embedded region, neighboring additives cancontact one another in some embodiments. Such contact can be improvedusing longer aspect ratio additives, while maintaining a relatively lowsurface area coverage for desired transparency. In some embodiments,contact between additives, such as nanowires, nanoparticles, microwires,and microparticles, can be increased through pressure (e.g., a calendarpress), sintering, or annealing, such as low temperature sintering attemperatures of about 50° C., about 125° C., about 150° C., about 175°C., or about 200° C., or in the range of about 50° C. to about 125° C.,about 100° C. to about 125° C., about 125° C. to about 150° C., about150° C. to about 175° C., or about 175° C. to about 200° C., flashsintering, sintering through the use of redox reactions to causedeposits onto additives to grow and fuse the additives together, or anycombination thereof. For example, in the case of silver or goldadditives, silver ions or gold ions can be deposited onto the additivesto cause the additives to fuse with neighboring additives. Hightemperature sintering at temperatures at or above about 200° C. is alsocontemplated. It is also contemplated that little or no contact isneeded for certain applications and devices, where charge tunneling orhopping provides sufficient electrical conductivity in the absence ofactual contact, or where a host material or a coating on top of the hostmaterial may itself be electrically conductive or semiconducting. Suchapplications and devices can operate with a sheet resistance up to about10⁶ Ω/sq or more. Individual additives can be separated by electricaland quantum barriers for electron transfer.

Transparent conductors described herein can be quite durable. In someembodiments, such durability is in combination with rigidity androbustness, and, in other embodiments, such durability is in combinationwith the ability to be flexed, rolled, bent, and folded, amongst otherphysical actions, with, for example, no greater than about 50%, nogreater than about 40%, no greater than about 30%, no greater than about20%, no greater than about 15%, no greater than about 10%, no greaterthan about 5%, no greater than about 3%, or substantially no decrease intransmittance, and no greater than about 50%, no greater than about 40%,no greater than about 30%, no greater than about 20%, no greater thanabout 15%, no greater than about 10%, no greater than about 5%, nogreater than about 3%, or substantially no increase in resistance (e.g.,surface or sheet resistance). In some embodiments, the transparentconductors can survive a standard test for adhesion of coatings (e.g., aScotch Tape Test) used in the coatings industry and yield substantiallyno decrease, or no greater than about 5% decrease, no greater than about10% decrease, no greater than about 15% decrease, no greater than about20% decrease, no greater than about 30% decrease, no greater than about40% decrease, or no greater than about 50% decrease in observedtransmittance, and yield substantially no increase, or no greater thanabout 5% increase, no greater than about 10% increase, no greater thanabout 15% increase, no greater than about 20% increase, no greater thanabout 30% increase, no greater than about 40% increase, or no greaterthan about 50% increase in observed resistance (e.g., sheet resistance).In some embodiments, the transparent conductors can also surviverubbing, scratching, flexing, physical abrasion, thermal cycling (e.g.,exposure to temperatures up to (or at least) about 600° C., up to (or atleast) about 550° C., up to (or at least) about 500° C., up to (or atleast) about 450° C., or up to (or at least) about 400° C.), chemicalexposure, accelerated life test (“ALT”), and humidity cycling withsubstantially no decrease, no greater than about 50% decrease, nogreater than about 40% decrease, no greater than about 30% decrease, nogreater than about 20% decrease, no greater than about 15% decrease, nogreater than about 10% decrease, no greater than about 5% decrease, orno greater than about 3% decrease in observed transmittance, and withsubstantially no increase, no greater than about 50% increase, nogreater than about 40% increase, no greater than about 30% increase, nogreater than about 20% increase, no greater than about 15% increase, nogreater than about 10% increase, no greater than about 5% increase, orno greater than about 3% increase in observed resistance (e.g., sheetresistance). This enhanced durability can result from embedding orincorporation of additives within at least a portion of a host material,such that the additives are physically or chemically held inside thehost material by molecular chains or other components of the hostmaterial. In some cases, flexing or pressing can be observed to increaseconductivity.

Various standard tests can be used to measure durability, such as interms of abrasion resistance. One such test, among others, isASTM-F735-06 Standard Test Method for Abrasion Resistance of TransparentPlastics and Coatings Using the Oscillating Sand Method. Another testthat can be used is ASTM D1044-08 Standard Test Method for Resistance ofTransparent Plastics to Surface Abrasion. Yet another possible standardtest is ASTM D4060-10 Standard Test Method for Abrasion Resistance ofOrganic Coatings by the Taber Abraser. Additional standard tests thatcan be used include tests for hardness, such as ASTM D3363-05 (2011)e1Standard Test Method for Film Hardness by Pencil Test, ASTM E384, ASTME10, ASTM B277-95 Standard Test Method for Hardness of ElectricalContact Materials, and ASTM D2583-06 Standard Test Method forIndentation Hardness of Rigid Plastics by Means of a Barcol Impressor.Further details on these tests are available from ASTM International ofWest Conshohocken, Pa. Other standardized protocols include the ISO15184, JIS K-5600, ECCA-T4-1, BS 3900-E19, SNV 37113, SIS 184187, NCN5350, and MIL C 27 227.

Another set of tests can be used to measure and evaluate reliabilityunder ALT conditions. Some industry standards include dry heat (e.g.,85° C./dry), moist heat (e.g., 60° C./90% RH, or 85° C./85° RH), drycold (e.g., −30° C./dry), thermal shock (e.g., 80° C.← → 40° C. cyclefor 30 minutes each). These ALT conditions can be carried out overhours, days, weeks, or months with samples exposed to those conditionsfor extended periods of time or number of cycles. In certain embodimentsof the transparent conductors disclosed herein, the change in sheetresistance, transparency, and/or haze are controlled within +/−50%, inother cases +/−25%, in other cases +/−10%, and in other cases +/−5%, orlower.

Another aspect of some embodiments of transparent conductors is that anelectrical percolation threshold can be attained using a lesser amountof additives. Stated in another way, electrical conductivity can beattained using less additive material, thereby saving additive materialand associated cost and increasing transparency. As will be understood,an electrical percolation threshold is typically reached when asufficient amount of additives is present to allow percolation ofelectrical charge from one additive to another additive, therebyproviding a conductive path across at least portion of a network ofadditives. In some embodiments, an electrical percolation threshold canbe observed via a change in slope of a logarithmic plot of resistanceversus loading level of additives. A lesser amount of additive materialcan be used since additives are largely confined to a “planar” or“planar-like” embedded region in some embodiments, thereby greatlyreducing topological disorder and resulting in a higher probability ofinter-additive (e.g., inter-nanowire or inter-nanotube) junctionformation. In other words, because the additives are confined to a thinembedded region in at least a portion of the host material, as opposedto dispersed throughout the thickness of the host material, theprobability that the additives will interconnect and form junctions canbe greatly increased. A lesser amount of additive material also can beused in embodiments where a host material is itself electricallyconductive or semiconducting. In some embodiments, an electricalpercolation threshold can be attained at a loading level of additives inthe range of about 0.001 μg/cm² to about 100 μg/cm² (or higher), such asfrom about 0.01 μg/cm² to about 100 μg/cm², from about 10 μg/cm² toabout 100 μg/cm², from 0.01 μg/cm² to about 0.4 μg/cm², from about 0.5μg/cm² to about 5 μg/cm², or from about 0.8 μg/cm² to about 3 μg/cm² forcertain additives such as silver nanowires. These loading levels can bevaried according to dimensions, material type, spatial dispersion, andother characteristics of additives.

In addition, a lesser amount of additives can be used (e.g., asevidenced by a thickness of an embedded region) to achieve anetwork-to-bulk transition, which is a parameter representing atransition of a thin layer from exhibiting effective material propertiesof a sparse two-dimensional conducting network to one exhibitingeffective properties of a three-dimensional conducting bulk material. Byconfining additives to a “planar” or “planar-like” embedded region, alower sheet resistance can be attained at specific levels oftransmittance. Furthermore, in some embodiments, carrier recombinationcan be reduced due to the reduction or elimination of interfacialdefects associated with a separate coating or other secondary materialinto which additives are mixed.

To expound further on these advantages, a network of additives can becharacterized by a topological disorder and by contact resistance.Topologically, above a critical density of additives and above acritical density of additive-additive (e.g., nanowire-nanowire,nanotube-nanotube, or nanotube-nanowire) junctions, electrical currentcan readily flow from a source to a drain. A “planar” or “planar-like”network of additives can reach a network-to-bulk transition with areduced thickness, represented in terms of a characteristic dimension ofthe additives (e.g., for nanowires, relative to a diameter of anindividual nanowire or an average diameter across the nanowires). Forexample, an embedded region can have a thickness up to about 10 times(or more) the characteristic dimension, such as up to about 9 times, upto about 8 times, up to about 7 times, up to about 6 times, up to about5 times, up to about 4 times, up to about 3 times, or up to about 2times the characteristic dimension, and down to about 0.05, about 0.1,about 0.2, about 0.3, about 0.4, or about 0.5 times the characteristicdimension, allowing devices to be thinner while increasing opticaltransparency and electrical conductivity. Accordingly, the transparentconductors described herein provide, in some embodiments, an embeddedregion with a thickness up to about n×d (in terms of nm) within whichare localized additives having a characteristic dimension of d (in termsof nm), where n=2, 3, 4, 5, or higher.

Another advantage of some embodiments of transparent conductors is that,for a given level of electrical conductivity, the transparent conductorscan yield higher transparency. This is because less additive materialcan be used to attain that level of electrical conductivity, in view ofthe efficient formation of additive-additive junctions for a givenloading level of additives, in view of the use of a host material thatis itself electrically conductive or semiconducting, or both. As will beunderstood, a transmittance of a thin conducting material (e.g., in theform of a film) can be expressed as a function of its sheet resistanceR_(□) and an optical wavelength, as given by the following approximaterelation for a thin film:

${T(\lambda)} = \left( {1 + {\frac{188.5}{R_{\bullet}}\frac{\sigma_{Op}(\lambda)}{\sigma_{DC}}}} \right)^{- 2}$where σ_(Op) and σ_(DC) are the optical and DC conductivities of thematerial, respectively. In some embodiments, silver nanowire networkssurface-embedded or otherwise incorporated into flexible transparentsubstrates can have sheet resistances as low as about 3.2 Ω/sq or about0.2 Ω/sq, or even lower. In other embodiments, transparent conductorscan reach up to about 85% (or more) for human vision orphotometric-weighted transmittance T (e.g., from about 350 nm to about700 nm) and sheet resistances as low as about 20 Ω/sq (or below). Instill other embodiments, a sheet resistance of ≦10 Ω/sq at ≧85% (e.g.,at least about 85%, at least about 90%, or at least about 95%, and up toabout 97%, about 98%, or more) human vision transmittance can beobtained with the transparent conductors. It will be understood thattransmittance can be measured relative to other ranges of opticalwavelength, such as transmittance at a given wavelength or range ofwavelengths in the visible range, such as about 550 nm, a solar-fluxweighted transmittance, transmittance at a given wavelength or range ofwavelengths in the infrared range, and transmittance at a givenwavelength or range of wavelengths in the ultraviolet range. It willalso be understood that transmittance can be measured relative to asubstrate (if present) (e.g., the transmittance value would not includethe transmittance loss from an underlying substrate that is below a hostmaterial that includes additives), or can be measured relative to air(e.g., the transmittance value would include the transmittance loss froman underlying substrate). Unless otherwise specified herein,transmittance values are designated relative to a substrate (ifpresent), although similar transmittance values (albeit with somewhathigher values) are also contemplated when measured relative to air.Also, it will also be understood that transmittance or another opticalcharacteristic can be measured relative to an overcoat, such as anoptically clear adhesive (if present) (e.g., the transmittance valuewould not include the transmittance loss from an overcoat overlying ahost material that includes additives), or can be measured relative toair (e.g., the transmittance value would include the transmittance lossfrom an overlying overcoat). Unless otherwise specified herein, valuesof optical characteristics are designated relative to an overlyingovercoat (if present), although similar values are also contemplatedwhen measured relative to air. For some embodiments, a DC-to-opticalconductivity ratio of transparent conductors can be at least about 100,at least about 115, at least about 300, at least about 400, or at leastabout 500, and up to about 600, up to about 800, or more.

Certain transparent conductors can include additives of nanowires (e.g.,silver nanowires) of average diameter in the range of about 1 nm toabout 100 nm, about 10 nm to about 80 nm, about 20 nm to about 80 nm, orabout 25 nm to about 45 nm, and an average length in the range of about50 nm to about 1,000 μm, about 50 nm to about 500 μm, about 100 nm toabout 100 μm, about 500 nm to 50 μm, about 5 μm to about 50 μm, about μmto about 150 μm, about 5 μm to about 35 μm, about 25 μm to about 80 μm,about 25 μm to about 50 μm, or about 25 μm to about 40 μm. A top of anembedded region can be located about 0 nm to about 100 μm below a top,embedding surface of a host material, such as about 0.0001 nm to about100 μm below the embedding surface, about 0.01 nm to about 100 μm belowthe embedding surface, about 0.1 nm to 100 μm below the embeddingsurface, about 0.1 nm to about 5 μm below the embedding surface, about0.1 nm to about 3 μm below the embedding surface, about 0.1 nm to about1 μm below the embedding surface, or about 0.1 nm to about 500 nm belowthe embedding surface. Nanowires embedded or incorporated into a hostmaterial can protrude from an embedding surface from about 0% by volumeand up to about 90%, up to about 95%, or up to about 99% by volume. Forexample, in terms of a volume of a nanowire exposed above the embeddingsurface relative to a total volume of the nanowire, at least onenanowire can have an exposed volume percentage (or a population of thenanowires can have an average exposed volume percentage) of up to about1%, up to about 5%, up to about 20%, up to about 50%, or up to about 75%or about 95%. At a transmittance of about 85% or greater (e.g., humanvision transmittance or one measured at another range of opticalwavelengths), a sheet resistance can be no greater than about 500 Ω/sq,no greater than about 400 Ω/sq, no greater than about 350 Ω/sq, nogreater than about 300 Ω/sq, no greater than about 200 Ω/sq, no greaterthan about 100 Ω/sq, no greater than about 75 Ω/sq, no greater thanabout 50 Ω/sq, no greater than about 25 Ω/sq, no greater than about 20Ω/sq, no greater than about 15 Ω/sq, no greater than about 10 Ω/sq, anddown to about 1 Ω/sq or about 0.1 Ω/sq, or less. At a transmittance ofabout 90% or greater, a sheet resistance can be no greater than about500 Ω/sq, no greater than about 400 Ω/sq, no greater than about 350Ω/sq, no greater than about 300 Ω/sq, no greater than about 200 Ω/sq, nogreater than about 100 Ω/sq, no greater than about 75 Ω/sq, no greaterthan about 50 Ω/sq, no greater than about 25 Ω/sq, no greater than about20 Ω/sq, no greater than about 15 Ω/sq, no greater than about 10 Ω/sq,and down to about 1 Ω/sq or less.

Certain transparent conductors can include additives of nanotubes (e.g.,either, or both, MWCNT and SWCNT) of average outer diameter in the rangeof about 1 nm to about 100 nm, about 1 nm to about 10 nm, about 10 nm toabout 50 nm, about 10 nm to about 80 nm, about 20 nm to about 80 nm, orabout 40 nm to about 60 nm, and an average length in the range of about50 nm to about 100 μm, about 100 nm to about 100 μm, about 500 nm to 50μm, about 5 μm to about 50 μm, about 5 μm to about 35 μm, about 25 μm toabout 80 μm, about 25 μm to about 50 μm, or about 25 μm to about 40 μm.A top of an embedded region can be located about 0 nm to about 100 μmbelow a top, embedding surface of a host material, such as about 0.01 nmto about 100 μm below the embedding surface, about 0.1 nm to 100 μmbelow the embedding surface, about 0.1 nm to about 5 μm below theembedding surface, about 0.1 nm to about 3 μm below the embeddingsurface, about 0.1 nm to about 1 μm below the embedding surface, orabout 0.1 nm to about 500 nm below the embedding surface. Nanotubesembedded or incorporated into a host material can protrude from anembedding surface from about 0% by volume and up to about 90%, up toabout 95%, or up to about 99% by volume. For example, in terms of avolume of a nanotube exposed above the embedding surface relative to atotal volume of the nanotube (e.g., as defined relative to an outerdiameter of a nanotube), at least one nanotube can have an exposedvolume percentage (or a population of the nanotubes can have an averageexposed volume percentage) of up to about 1%, up to about 5%, up toabout 20%, up to about 50%, or up to about 75% or about 95%. At atransmittance of about 85% or greater (e.g., human vision transmittanceor one measured at another range of optical wavelengths), a sheetresistance can be no greater than about 500 Ω/sq, no greater than about400 Ω/sq, no greater than about 350 Ω/sq, no greater than about 300Ω/sq, no greater than about 200 Ω/sq, no greater than about 100 Ω/sq, nogreater than about 75 Ω/sq, no greater than about 50 Ω/sq, no greaterthan about 25 Ω/sq, no greater than about 20 Ω/sq, no greater than about15 Ω/sq, no greater than about 10 Ω/sq, and down to about 1 Ω/sq orless. At a transmittance of about 90% or greater, a sheet resistance canbe no greater than about 500 Ω/sq, no greater than about 400 Ω/sq, nogreater than about 350 Ω/sq, no greater than about 300 Ω/sq, no greaterthan about 200 Ω/sq, no greater than about 100 Ω/sq, no greater thanabout 75 Ω/sq, no greater than about 50 Ω/sq, no greater than about 25Ω/sq, no greater than about 20 Ω/sq, no greater than about 15 Ω/sq, nogreater than about 10 Ω/sq, and down to about 1 Ω/sq or about 0.1 Ω/sq,or less.

In the case of a patterned transparent conductor, multiple embeddedregions can be located across a single host material or across multiplehost materials according to a pattern. The characteristics and rangesset forth herein regarding the nature and extent of surface embeddinggenerally can apply across the multiple embedded regions, although theparticular nature and extent of surface embedding can vary across theembedded regions to create a spatially varying contrast in electricalconductivity.

Surface Embedding Process

The transparent conductors described herein can be formed according tomanufacturing methods that can be carried out in a highly-scalable,rapid, and low-cost fashion, in which additives are durably incorporatedinto a wide variety of host materials. Some embodiments of themanufacturing methods can be generally classified into two categories:(1) surface embedding additives into a dry composition to yield a hostmaterial with the surface-embedded additives; and (2) surface embeddingadditives into a wet composition to yield a host material with thesurface-embedded additives. It will be understood that suchclassification is for ease of presentation, and that “dry” and “wet” canbe viewed as relative terms (e.g., with varying degrees of dryness orwetness), and that the manufacturing methods can apply to a continuumspanned between fully “dry” and fully “wet.” Accordingly, processingconditions and materials described with respect to one category (e.g.,dry composition) can also apply with respect to another category (e.g.,wet composition), and vice versa. It will also be understood thathybrids or combinations of the two categories are contemplated, such aswhere a wet composition is dried or otherwise converted into a drycomposition, followed by surface embedding of additives into the drycomposition to yield a host material with the surface-embeddedadditives. It will further be understood that, although “dry” and “wet”sometimes may refer to a level of water content or a level of solventcontent, “dry” and “wet” also may refer to another characteristic of acomposition in other instances, such as a degree of cross-linking orpolymerization.

Attention first turns to FIG. 2A and FIG. 2B, which illustrates examplesof manufacturing methods for surface embedding additives into drycompositions, according to embodiments of the invention.

By way of overview, the illustrated embodiments involve the applicationof an embedding fluid to allow additives to be embedded into a drycomposition. In general, the embedding fluid serves to reversibly alterthe state of the dry composition, such as by dissolving, reacting,softening, solvating, swelling, or any combination thereof, therebyfacilitating embedding of the additives into the dry composition. Forexample, the embedding fluid can be specially formulated to act as aneffective solvent for a polymer, while possibly also being modified withstabilizers (e.g., dispersants) to help suspend the additives in theembedding fluid. The embedding fluid also can be specially formulated toreduce or eliminate problems with solvent/polymer interaction, such ashazing, crazing, and blushing. The embedding fluid can include a solventor a solvent mixture that is optimized to be low-cost, Volatile OrganicCompound (“VOC”)-free, VOC-exempt or low-VOC, Hazardous Air Pollutant(“HAP”)-free, non-ozone depleting substances (“non-ODS”), low volatilityor non-volatile, and low hazard or non-hazardous. As another example,the dry composition can include a ceramic or a ceramic precursor in theform of a gel or a semisolid, and application of the embedding fluid cancause the gel to be swollen by filling pores with the fluid, byelongation of partially uncondensed oligomeric or polymeric chains, orboth. As a further example, the dry composition can include a ceramic ora ceramic precursor in the form of an ionic polymer, such as sodiumsilicate or another alkali metal silicate, and application of theembedding fluid can dissolve at least a portion of the ionic polymer toallow embedding of the additives. The embedding of the additives is thenfollowed by hardening or other change in state of the softened orswelled composition, resulting in a host material having the additivesembedded therein. For example, the softened or swelled composition canbe hardened by exposure to ambient conditions, or by cooling thesoftened or swelled composition. In other embodiments, the softened orswelled composition is hardened by evaporating or otherwise removing atleast a portion of the embedding fluid (or other liquid or liquid phasethat is present), applying airflow, applying a vacuum, or anycombination thereof. In the case of a ceramic precursor, curing can becarried out after embedding such that the ceramic precursor is convertedinto a glass or another ceramic. Curing can be omitted, depending on theparticular application. Depending on the particular ceramic precursor(e.g., a silane), more or less heat can be involved to achieve variousdegrees of curing or conversion into a fully reacted or fully formedglass.

Referring to FIG. 2A, a dry composition 200 can be provided in the formof a sheet, a film, or other suitable form. The dry composition 200 cancorrespond to a host material and, in particular, can include anymaterial previously listed as suitable host materials. It is alsocontemplated that the dry composition 200 can correspond to a hostmaterial precursor, which can be converted into the host material bysuitable processing, such as drying, curing, cross-linking,polymerizing, or any combination thereof. In some embodiments, the drycomposition 200 can include a material with a solid phase as well as aliquid phase, or can include a material that is at least partially solidor has properties resembling those of a solid, such as a semisolid, agel, and the like. Next, and referring to FIG. 2A, additives 202 and anembedding fluid 204 are applied to the dry composition 200. Theadditives 202 can be in solution or otherwise dispersed in the embeddingfluid 204, and can be simultaneously applied to the dry composition 200via one-step embedding. Alternatively, the additives 202 can beseparately applied to the dry composition 200 before, during, or afterthe embedding fluid 204 treats the dry composition 200. Embedding thatinvolves separate application of the additives 202 and the embeddingfluid 204 can be referred as two-step embedding. Subsequently, theresulting host material 206 has at least some of the additives 202partially or fully embedded into a surface of the host material 206.Optionally, suitable processing can be carried out to convert thesoftened or swelled composition 200 into the host material 206. Duringdevice assembly, the host material 206 with the embedded additives 202can be laminated or otherwise connected to adjacent device layers, orcan serve as a substrate onto which adjacent device layers are formed,laminated, or otherwise applied.

In the case of a patterned transparent conductor, surface embeddingaccording to FIG. 2A can be carried out generally uniformly across thedry composition 200, followed by spatially selective or varyingtreatment to yield higher conductance and lower conductance portionsacross the host material 206. Alternatively, or in conjunction, surfaceembedding according to FIG. 2A can be carried out in a spatiallyselective or varying manner, such as by applying the additives 202 in aspatially selective or varying manner, by applying the embedding fluid204 in a spatially selective or varying manner, or both.

FIG. 2B is a process flow similar to FIG. 2A, but with a dry composition208 provided in the form of a coating or layer that is disposed on topof a substrate 210. The dry composition 208 can correspond to a hostmaterial, or can correspond to a host material precursor, which can beconverted into the host material by suitable processing, such as drying,curing, cross-linking, polymerizing, or any combination thereof. Othercharacteristics of the dry composition 208 can be similar to thosedescribed above with reference to FIG. 2A, and are not repeated below.Referring to FIG. 2B, the substrate 210 can be transparent or opaque,can be flexible or rigid, and can be comprised of, for example, apolymer, an ionomer, a coated polymer (e.g., a PET film with a PMMAhardcoat), ethylene vinyl acetate (or EVA), cyclic olefin polymer (orCOP), cyclic olefin copolymer (or COC), polyvinyl butyral (or PVB),thermoplastic olefin (or TPO), thermoplastic polyurethane (or TPU),polyethylene (or PE), polyethylene terephthalate (or PET), polyethyleneterephthalate glycol (or PETG), polycarbonate, polyvinyl chloride (orPVC), polypropylene (or PP), acrylic-based polymer, acrylonitrilebutadiene styrene (or ABS), ceramic, glass, silicon, metal (e.g.,stainless steel or aluminum), or any combination thereof, as well as anyother material previously listed as suitable host materials. Thesubstrate 210 can serve as a temporary substrate that is subsequentlyremoved during device assembly, or can be retained in a resulting deviceas a layer or other component of the device. Next, additives 212 and anembedding fluid 214 are applied to the dry composition 208. Theadditives 212 can be in solution or otherwise dispersed in the embeddingfluid 214, and can be simultaneously applied to the dry composition 208via one-step embedding. Alternatively, the additives 212 can beseparately applied to the dry composition 208 before, during, or afterthe embedding fluid 214 treats the dry composition 208. As noted above,embedding involving the separate application of the additives 212 andthe embedding fluid 214 can be referred as two-step embedding.Subsequently, the resulting host material 216 (which is disposed on topof the substrate 210) has at least some of the additives 212 partiallyor fully embedded into a surface of the host material 216. Optionally,suitable processing can be carried out to convert the softened orswelled composition 208 into the host material 216. During deviceassembly, the host material 216 with the embedded additives 212 can belaminated or otherwise connected to adjacent device layers, or can serveas a substrate onto which adjacent device layers are formed, laminated,or otherwise applied.

In the case of a patterned transparent conductor, surface embeddingaccording to FIG. 2B can be carried out generally uniformly across thedry composition 208, followed by spatially selective or varyingtreatment to yield higher conductance and lower conductance portionsacross the host material 216. Alternatively, or in conjunction, surfaceembedding according to FIG. 2B can be carried out in a spatiallyselective or varying manner, such as by disposing or forming the drycomposition 208 in a spatially selective or varying manner over thesubstrate 210, by applying the additives 212 in a spatially selective orvarying manner across either, or both, of the dry composition 208 andthe substrate 210, by applying the embedding fluid 214 in a spatiallyselective or varying manner across either, or both, of the drycomposition 208 and the substrate 210, or any combination thereof.

In some embodiments, additives are dispersed in an embedding fluid, ordispersed in a separate carrier fluid and separately applied to a drycomposition. Dispersion can be accomplished by mixing, milling,sonicating, shaking (e.g., wrist action shaking, rotary shaking),vortexing, vibrating, flowing, chemically modifying the additives'surfaces, chemically modifying a fluid, increasing the viscosity of thefluid, adding a dispersing or suspending agent to the fluid, adding astabilization agent to the fluid, changing the polarity of the fluid,changing the hydrogen bonding of the fluid, changing the pH of thefluid, or otherwise processing the additives to achieve the desireddispersion. The dispersion can be uniform or non-uniform, and can bestable or unstable. A carrier fluid can serve as an embedding fluid(e.g., an additional embedding fluid), or can have similarcharacteristics as an embedding fluid. In other embodiments, a carrierfluid can serve as a transport medium to carry or convey additives, butis otherwise substantially inert towards the additives and the drycomposition.

Fluids (e.g., embedding fluids and carrier fluids) can include liquids,gases, or supercritical fluids. Combinations of different types offluids are also suitable. Fluids can include one or more solvents. Forexample, a fluid can include water, an ionic or ion-containing solution,an ionic liquid, an organic solvent (e.g., a polar, organic solvent; anon-polar, organic solvent; an aprotic solvent; a protic solvent; apolar aprotic solvent, or a polar, protic solvent); an inorganicsolvent, or any combination thereof. Oils also can be consideredsuitable fluids. Salts, surfactants, dispersants, stabilizers, polymers,monomers, oligomers, cross-linking agents, polymerization agents, acids,bases, or binders can also be included in the fluids.

Examples of suitable organic solvents include 2-methyltetrahydrofuran, achloro-hydrocarbon, a fluoro-hydrocarbon, a ketone, a paraffin,acetaldehyde, acetic acid, acetic anhydride, acetone, acetonitrile, analkyne, an olefin, aniline, benzene, benzonitrile, benzyl alcohol,benzyl ether, butanol, butanone, butyl acetate, butyl ether, butylformate, butyraldehyde, butyric acid, butyronitrile, carbon disulfide,carbon tetrachloride, chlorobenzene, chlorobutane, chloroform,cycloaliphatic hydrocarbons, cyclohexane, cyclohexanol, cyclohexanone,cyclopentanone, cyclopentyl methyl ether, diacetone alcohol,dichloroethane, dichloromethane, diethyl carbonate, diethyl ether,diethylene glycol, diglyme, di-isopropylamine, dimethoxyethane, dimethylformamide, dimethyl sulfoxide, dimethylamine, dimethylbutane,dimethylether, dimethylformamide, dimethylpentane, dimethylsulfoxide,dioxane, dodecafluoro-1-heptanol, ethanol, ethyl acetate, ethyl ether,ethyl formate, ethyl propionate, ethylene dichloride, ethylene glycol,formamide, formic acid, glycerine, heptane, hexafluoroisopropanol (orHFIP), hexamethylphosphoramide, hexamethyl phosphorous triamide, hexane,hexanone, hydrogen peroxide, hypochlorite, i-butyl acetate, i-butylalcohol, i-butyl formate, i-butylamine, i-octane, i-propyl acetate,i-propyl ether, isopropanol, isopropylamine, ketone peroxide, methanoland calcium chloride solution, methanol, methoxyethanol, methyl acetate,methyl ethyl ketone (or MEK), methyl formate, methyl n-butyrate, methyln-propyl ketone, methyl t-butyl ether, methylene chloride, methylene,methylhexane, methylpentane, mineral oil, m-xylene, n-butanol, n-decane,n-hexane, nitrobenzene, nitroethane, nitromethane, nitropropane,2-N-methyl-2-pyrrolidinone, n-propanol, octafluoro-1-pentanol, octane,pentane, pentanone, petroleum ether, phenol, propanol, propionaldehyde,propionic acid, propionitrile, propyl acetate, propyl ether, propylformate, propylamine, propylene glycol, p-xylene, pyridine, pyrrolidine,t-butanol, t-butyl alcohol, t-butyl methyl ether, tetrachloroethane,tetrafluoropropanol (or TFP), tetrahydrofuran (or THF),tetrahydronaphthalene, toluene, triethyl amine, trifluoroacetic acid,trifluoroethanol (or TFE), trifluoropropanol, trimethylbutane,trimethylhexane, trimethylpentane, valeronitrile, xylene, xylenol, orany combination thereof. Alcohols including from one to ten carbon atoms(i.e., C₁-C₁₀ alcohols, such as C₁-C₆ alcohols) can be consideredsuitable, such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol,2-butanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-pentanol,2-pentanol, 3-pentanol, 2-2-dimethyl-1-propanol, 1-hexanol, as well ascombinations, functionalized forms, and mixtures thereof with anotherfluid such as water. Alcohols include primary alcohols (e.g., n-propylalcohol, isobutyl alcohol), secondary alcohols (e.g., isopropyl alcohol,cyclohexanol), tertiary alcohols (e.g., tert-amyl alcohol), or anycombination thereof. Other examples of suitable alcohols includemonohydric alcohols (e.g., methanol, ethanol, isopropyl alcohol, butylalcohol, butanol, pentanol, hexadecan-1-ol, amyl alcohol, cetylalcohol), polyhydric alcohols (e.g., ethylene glycol, glycerin,Butan-1,2,3,4-tetraol, erythritol, Pentane-1,2,3,4,5-pentol, xylitol,Hexane-1,2,3,4,5,6-hexyl, mannitol, sorbitol,Heptane-1,2,3,4,5,6,7-heptol, volemitol), unsaturated aliphatic alcohols(e.g., Prop-2-ene-1-ol, allyl alcohol, 3,7-Dimethyloca-2,6-dien-1-ol,Geraniol, prop-2-in-1-ol, propargyl alcohol), alicyclic alcohols (e.g.,cyclohexane-1,2,3,4,5,6-hexyl, inositol,2-(2-propyl)-5-methyl-cyclohexane-1-ol, Menthol), as well ascombinations, functionalized forms, and mixtures thereof with otherfluids (e.g., water).

Suitable inorganic solvents include, for example, water, ammonia, sodiumhydroxide, sulfur dioxide, sulfuryl chloride, sulfuryl chloridefluoride, phosphoryl chloride, phosphorus tribromide, dinitrogentetroxide, antimony trichloride, bromine pentafluoride, hydrogenfluoride, or any combination thereof.

Suitable ionic solutions include, for example, choline chloride, urea,malonic acid, phenol, glycerol, 1-alkyl-3-methylimidazolium,1-alkylpyridinium, N-methyl-N-alkylpyrrolidinium,1-butyl-3-methylimidazolium hexafluorophosphate, ammonium, choline,imidazolium, phosphonium, pyrazolium, pyridinium, pyrrolidinium,sulfonium, 1-ethyl-1-methylpiperidinium methyl carbonate,4-ethyl-4-methylmorpholinium methyl carbonate, or any combinationthereof. Other methylimidazolium solutions can be considered suitable,including 1-ethyl-3-methylimidazolium acetate,1-butyl-3-methylimidazolium tetrafluoroborate,1-n-butyl-3-methylimidazolium tetrafluoroborate,1-butyl-3-methylimidazolium hexafluorophosphate,1-n-butyl-3-methylimidazoliumhexafluoro phosphate,1-butyl-3-methylimidazolium 1,1,1-trifluoro-N[(trifluoromethyl)sulfonyl]methanesulfonamide,1-butyl-3-methylimidazolium bis(trifluoro methylsulfonyl)imide,1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide, and1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, or anycombination thereof.

Other suitable fluids include halogenated compounds, imides, and amides,such as N-ethyl-N,N-bis(1-methylethyl)-1-heptanaminiumbis[(trifluoromethyl)sulfonyl]imide, ethylheptyl-di-(1-methylethyl)ammonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methane sulfonamide,ethylheptyl-di-(1-methyl ethyl)ammoniumbis(trifluoromethylsulfonyl)imide,ethylheptyl-di-(1-methylethyl)ammoniumbis[(trifluoromethyl)sulfonyl]amide, or any combination thereof. A fluidcan also include ethylheptyl-di-(1-methylethyl)ammoniumbis[(trifluoromethyl)sulfonyl]imide, N₅N₅N-tributyl-1-octanaminiumtrifluoromethane sulfonate, tributyloctylammonium triflate,tributyloctylammonium trifluoromethanesulfonate,N,N,N-tributyl-1-hexanaminium bis[(trifluoromethyl)sulfonyl]imide,tributylhexylammonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide,tributylhexylammonium bis(trifluoromethylsulfonyl)imide,tributylhexylammonium bis[(trifluoromethyl)sulfonyl]amide,tributylhexylammonium bis[(trifluoromethyl)sulfonyl]imide,N,N,N-tributyl-1-heptanaminium bis[(trifluoromethyl)sulfonyl]imide,tributylheptylammonium 1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide, tributylheptylammoniumbis(trifluoromethylsulfonyl)imide; tributylheptylammoniumbis[(trifluoromethyl)sulfonyl]amide, tributylheptylammoniumbis[(trifluoromethyl)sulfonyl]imide, N,N,N-tributyl-1-octanaminiumbis[(trifluoromethyl) sulfonyl]imide, tributyloctylammonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methane sulfonamide,tributyloctylammonium bis(trifluoromethylsulfonyl)imide,tributyloctylammonium bis[(trifluoromethyl)sulfonyl]amide,tributyloctylammonium bis[(trifluoromethyl)sulfonyl]imide,1-butyl-3-methylimidazolium trifluoroacetate,1-methyl-1-propylpyrrolidinium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide,1-methyl-1-propylpyrrolidinium bis(trifluoro methylsulfonyl)imide,1-methyl-1-propylpyrrolidinium bis[(trifluoromethyl)sulfonyl]amide,1-methyl-1-propylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide,1-butyl-1-methylpyrrolidinium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide,1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide,1-butyl-1-methylpyrrolidinium bis [(trifluoromethyl)sulfonyl]amide,1-butyl-1-methylpyrrolidinium bis[(trifluoromethyl)sulfonyl]imide,1-butylpyridinium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide,1-butylpyridinium bis(trifluoromethylsulfonyl)imide, 1-butylpyridiniumbis[(trifluoromethyl) sulfonyl]amide, 1-butylpyridiniumbis[(trifluoromethyl)sulfonyl]imide, 1-butyl-3-methyl imidazoliumbis(perfluoroethylsulfonyl)imide, butyltrimethylammoniumbis(trifluoromethyl sulfonyl)imide, 1-octyl-3-methylimidazolium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide,1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide,1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide,1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide,1-ethyl-3-methylimidazolium tetrafluoroborate,N₅N₅N-trimethyl-1-hexanaminium bis[(trifluoromethyl)sulfonyl]imide,hexyltrimethylammonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide,hexyltrimethylammonium bis(trifluoromethylsulfonyl)imide,hexyltrimethylammonium bis[(trifluoromethyl)sulfonyl]amide,hexyltrimethylammonium bis[(trifluoromethyl)sulfonyl]imide,N,N,N-trimethyl-1-heptanaminium bis[(trifluoromethyl)sulfonyl]imide,heptyltrimethylammonium1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide,heptyltrimethylammonium bis(trifluoro methylsulfonyl)imide,heptyltrimethylammonium bis[(trifluoromethyl)sulfonyl]amide,heptyltrimethylammonium bis[(trifluoromethyl)sulfonyl]imide,N,N,N-trimethyl-1-octanaminium bis[(trifluoromethyl)sulfonyl]imide,trimethyloctylammonium 1,1,1-trifluoro-N-[(trifluoromethyl)sulfonyl]methanesulfonamide, trimethyloctylammoniumbis(trifluoromethylsulfonyl)imide, trimethyloctylammoniumbis[(trifluoromethyl)sulfonyl]amide, trimethyloctylammoniumbis[(trifluoromethyl)sulfonyl]imide, 1-ethyl-3-methylimidazolium ethylsulfate, or any combination thereof.

Control over surface embedding of additives can be achieved through theproper balancing of the swelling-dispersion-evaporation-applicationstages. This balance can be controlled by, for example, a solvent-hostmaterial interaction parameter, sizes of additives, reactivity andvolatility of an embedding fluid, impinging additive momentum orvelocity, temperature, humidity, pressure, and others factors. Moreparticularly, examples of processing parameters for surface embeddingare listed below for some embodiments of the invention:

Embedding Fluid Selection:

-   -   Solubility parameter relative to the substrate or other host        material (e.g.    -   Hildebrand and Hansen solubility parameters)    -   Compatibility of embedding fluid with surface (e.g., matching or        comparison of dielectric constant, partition coefficient, pKa,        etc.)    -   Azeotropes, miscibility    -   Solvent diffusion/mobility    -   Viscosity    -   Evaporation (flash point, vapor pressure, cooling, etc.)    -   Duration of solvent exposure to substrate or other host material    -   Dispersants, surfactants, stabilizers, rheology modifiers    -   Solvent (VOC, VOC-exempt, VOC-free, aqueous based)        Substrate or Other Host Material:    -   Solubility parameters (relative to the solvent formulation)    -   Crystallinity    -   Degree of crosslinking    -   Molecular weight    -   Surface energy    -   Co-polymers/composite materials    -   Surface treatment        Additive Type:    -   Concentration of additives    -   Geometry of additives    -   Surface modification (e.g. ligands, surfactants) of additives    -   Stability of additives in the solvent formulation        Process Operations and Conditions:    -   Deposition Type/Application method (e.g., spraying, printing,        rolling coating, gravure coating, slot-die coating, capillary        coating, meniscus coating, cup coating, blade coating,        airbrushing, immersion, dip coating, etc.)    -   Duration of solvent exposure to substrate or other host material    -   Wetting, surface tension    -   Volume of solvent    -   Surface (pre)treatment    -   Humidity    -   Surface (post)treatment    -   Impact/momentum/velocity of additives onto surface (e.g., may        influence depth or extent of embedding)    -   Shear applied to solvent between host material and applicator    -   Post-processing conditions (e.g., heating, evaporation, fluid        removal, air-drying, etc.)        Other Factors:    -   Wetting/surface tension    -   Capillary forces, wicking    -   Amount of solvent applied to the surface    -   Duration of solvent exposure to the surface    -   Surface (pre)treatment    -   Stability of formulation    -   Diffusion of embedding fluid into surface: thermodynamic and        kinetics considerations        Mitigation of Undesired Effects:    -   Irreversible destruction    -   Long swelling/solubility time    -   Blushing, hazing    -   Cracking, crazing    -   Environmental conditions (e.g. humidity)    -   Permanent softening    -   Wettability/uneven wetting    -   Solution stability    -   Surface Roughness

Some, or all, of the aforementioned parameters can be altered orselected to tune a depth or an extent of embedding of additives into agiven host material. For example, higher degrees of embedding deep intoa surface of a host material can be achieved by increasing a solvencypower of an embedding fluid interacting with the host material, matchingclosely Hansen solubility parameters of the embedding fluid-substrate,prolonging the exposure duration of the embedding fluid in contact withthe host material, increasing an amount of the embedding fluid incontact with the host material, elevating a temperature of the system,increasing a momentum of additives impinging onto the host material,increasing a diffusion of either, or both, of the embedding fluid andthe additives into the host material, or any combination thereof.

Fluids (e.g., embedding fluids and carrier fluids) can also includesalts, surfactants, stabilizers, and other agents useful in conferring aparticular set of characteristics on the fluids. Stabilizers can beincluded based on their ability to at least partially inhibitinter-additive agglomeration. Other stabilizers can be chosen based ontheir ability to preserve the functionality of additives. Butylatedhydroxytoluene (or BHT), for instance, can act as a good stabilizer andas an antioxidant. Other agents can be used to adjust rheologicalproperties, evaporation rate, and other characteristics.

Fluids and additives can be applied so as to be largely stationaryrelative to a surface of a dry composition. In other embodiments,application is carried out with relative movement, such as by spraying afluid onto a surface, by conveying a dry composition through a fallingcurtain of a fluid, or by conveying a dry composition through a pool orbath of a fluid. Application of fluids and additives can be effected byairbrushing, atomizing, nebulizing, spraying, electrostatic spraying,pouring, rolling, curtaining, wiping, spin casting, dripping, dipping,painting, flowing, brushing, immersing, patterning (e.g., stamping,inkjet printing, controlled spraying, controlled ultrasonic spraying,and so forth), flow coating methods (e.g., slot die, capillary coating,meniscus coating, meyer rod, blade coating, cup coating, draw down, andthe like), printing, gravure printing, lithography, screen printing,flexo printing, offset printing, roll coating, inkjet printing, intaglioprinting, or any combination thereof. In some embodiments, additives arepropelled, such as by a sprayer, onto a surface, thereby facilitatingembedding by impact with the surface. In other embodiments, a gradientis applied to a fluid, additives, or both. Suitable gradients includemagnetic and electric fields. The gradient can be used to apply,disperse, or propel the fluid, additives, or both, onto a surface. Insome embodiments, the gradient is used to manipulate additives so as tocontrol the extent of embedding. An applied gradient can be constant orvariable. Gradients can be applied before a dry composition is softenedor swelled, while the dry composition remains softened or swelled, orafter the dry composition is softened or swelled. It is contemplatedthat a dry composition can be heated to achieve softening, and thateither, or both, a fluid and additives can be heated to promoteembedding. In some embodiments, embedding of additives can be achievedprimarily or solely through application of an embedding fluid, withoutrequiring application of gradients or external pressure. In someembodiments, embedding of additives can be achieved through applicationof pressure (e.g., pressure rollers) in place of, or in conjunctionwith, an embedding fluid.

Application of fluids and additives and embedding of the additives canbe spatially controlled to yield patterns. In some embodiments, spatialcontrol can be achieved with a physical mask, which can be placedbetween an applicator and a surface to block a segment of appliedadditives from contacting the surface, resulting in controlledpatterning of additive embedding. In other embodiments, spatial controlcan be achieved with a photomask. A positive or negative photomask canbe placed between a light source and a surface, which can correspond toa photoresist. Light transmitted through non-opaque parts of thephotomask can selectively affect a solubility of exposed parts of thephotoresist, and resulting spatially controlled soluble regions of thephotoresist can permit controlled embedding of additives. In otherembodiments, spatial control can be achieved through the use of electricgradients, magnetic gradients, electromagnetic fields, thermalgradients, pressure or mechanical gradients, surface energy gradients(e.g., liquid-solid-gas interfaces, adhesion-cohesion forces, andcapillary effects), printing, or any combination thereof. Spatialcontrol can also be achieved by printing a material that differs from ahost material and in which embedding does not occur (or is otherwiseinhibited). Further details on patterning are described below.

As noted above, additives can be dispersed in an embedding fluid, andapplied to a dry composition along with the embedding fluid via one-stepembedding. Additives also can be applied to a dry composition separatelyfrom an embedding fluid via two-step embedding. In the latter scenario,the additives can be applied in a wet form, such as by dispersing in acarrier fluid or by dispersing in the same embedding fluid or adifferent embedding fluid. Still in the latter scenario, the additivescan be applied in a dry form, such as in the form of aerosolized powder.It is also contemplated that the additives can be applied in a quasi-dryform, such as by dispersing the additives in a carrier fluid that isvolatile, such as methanol, another low boiling point alcohol, oranother low boiling point organic solvent, which substantially vaporizesprior to impact with a dry composition.

By way of example, one embodiment involves spraying, airbrushing, orotherwise atomizing a solution of nanowires or other additives dispersedin an appropriate carrier fluid onto a dry composition.

As another example, one embodiment involves pre-treating a drycomposition by spraying or otherwise contacting an embedding fluid withthe dry composition, and then, after the passage of time t₁, spraying orairbrushing nanowires or other additives with velocity such that thecombination of the temporarily softened dry composition and the velocityof the impinging nanowires allow rapid and durable surface-embedding ofthe nanowires. t₁ can be, for example, in the range of about 0nanosecond to about 24 hours, such as from about 1 nanosecond to about24 hours, from about 1 nanosecond to about 1 hour or from about 1 secondto about 1 hour. Two spray nozzles can be simultaneously or sequentiallyactivated, with one nozzle dispensing the embedding fluid, and the othernozzle dispensing, with velocity, atomized nanowires dispersed in acarrier fluid towards the dry composition. Air-curing or highertemperature annealing optionally can be included.

As another example, one embodiment involves spraying, airbrushing, orotherwise atomizing a solution of nanowires or other additives dispersedin a carrier fluid onto a dry composition. After the passage of time t₂,a second spraying, airbrushing, or atomizing operation is used to applyan embedding fluid so as to permit efficient surface-embedding of thenanowires. t₂ can be, for example, in the range of about 0 nanosecond toabout 24 hours, such as from about 1 nanosecond to about 24 hours, fromabout 1 nanosecond to about 1 hour or from about 1 second to about 1hour. Two spray nozzles can be simultaneously or sequentially activated,with one nozzle dispensing the embedding fluid, and the other nozzledispensing, with velocity, atomized nanowires dispersed in the carrierfluid towards the dry composition. Air-curing or higher temperatureannealing optionally can be included.

A time period for exposure or otherwise contacting an embedding fluidwith a dry composition can be selected, for example, according to adesired extent of embedding, while mitigating against undesired effectssuch as hazing, crazing, blushing, and so forth. In some embodiments, aexposure time can be, for example, in the range of about 0.1 second toabout 24 hours, such as from about 0.5 second to about 12 hours, fromabout 1 second to about 6 hours, from about 1 second to about 3 hours,from about 1 second to about 2 hours, from about 1 second to about 1hour, from about 1 minute to about 50 minutes, from about 1 minute toabout 40 minutes, from about 1 minute to about 30 minutes, or from about1 minute to about 20 minutes.

Attention next turns to FIG. 2C, which illustrates a manufacturingmethod for surface embedding additives 222 into a wet composition 218,according to an embodiment of the invention. Referring to FIG. 2C, thewet composition 218 is applied to a substrate 220 in the form of acoating or a layer that is disposed on top of the substrate 220. The wetcomposition 218 can correspond to a dissolved form of a host materialand, in particular, can include a dissolved form, a colloidal form, ananoparticle form, a sol-form of any material previously listed assuitable host materials. It is also contemplated that the wetcomposition 218 can correspond to a host material precursor, which canbe converted into the host material by suitable processing, such asdrying, curing, cross-linking, polymerizing, sintering, calcining, orany combination thereof. For example, the wet coating composition 218can be a coating or a layer that is not fully cured or set, across-linkable coating or layer that is not fully cross-linked, whichcan be subsequently cured or cross-linked using suitable polymerizationinitiators or cross-linking agents, or a coating or a layer of monomers,oligomers, or a combination of monomers and oligomers, which can besubsequently polymerized using suitable polymerization initiators orcross-linking agents. The wet composition 218 also can be patterned, forinstance, with printing methods like screen, reverse offset gravure,flexo, or ink-jet, printing, or another method. In some embodiments, thewet composition 218 can include a material with a liquid phase as wellas a solid phase, or can include a material that is at least partiallyliquid or has properties resembling those of a liquid, such as a sol, asemisolid, a gel, and the like. The substrate 220 can be transparent oropaque, can be flexible or rigid, and can be composed of, for example, apolymer, an ionomer, EVA, PVB, TPO, TPU, PE, PET, PETG, PMMA,polycarbonate, PVC, PP, acrylic-based polymer, ABS, ceramic, glass,silicon, metal (e.g., stainless steel or aluminum), or any combinationthereof, as well as any other material previously listed as suitablehost materials. The substrate 220 can serve as a temporary substratethat is subsequently removed during device assembly, or can be retainedin a resulting device as a layer or other component of the device.

Next, according to the option on the left-side of FIG. 2C, the additives222 are applied to the wet composition 218 prior to drying or while itremains in a state that permits embedding of the additives 222 withinthe wet composition 218. In some embodiments, application of theadditives 222 is via a flow coating method (e.g., slot die, capillarycoating, meyer rod, cup coating, draw down, and the like). Although notillustrated on the left-side, it is contemplated that an embedding fluidcan be simultaneously or separately applied to the wet composition 218to facilitate the embedding of the additives 222. In some embodiments,embedding of the additives 222 can be achieved through application ofpressure (e.g., pressure rollers) in place of, or in conjunction with,an embedding fluid. Subsequently, the resulting host material 224 has atleast some of the additives 222 partially or fully embedded into asurface of the host material 224. Suitable processing can be carried outto convert the wet composition 218 into the host material 224. Duringdevice assembly, the host material 224 with the embedded additives 222can be laminated or otherwise connected to adjacent device layers, orcan serve as a substrate onto which adjacent device layers are formed,laminated, or otherwise applied.

Certain aspects regarding the application of the additives 222 and theembedding of the additives 222 on the left-side of FIG. 2C can becarried out using similar processing conditions and materials asdescribed above for FIG. 2A and FIG. 2B, and those aspects need not berepeated below.

Referring to the option on the right-side of FIG. 2C, the wetcomposition 218 can be initially converted into a dry composition 226 bysuitable processing, such as by at least partially drying, curing,cross-linking, polymerization, or any combination thereof. Next, theadditives 222 and an embedding fluid 228 can be applied to the drycomposition 226. The additives 222 can be in solution or otherwisedispersed in the embedding fluid 228, and can be simultaneously appliedto the dry composition 226 via one-step embedding. Alternatively, theadditives 222 can be separately applied to the dry composition 226before, during, or after the embedding fluid 228 treats the drycomposition 226. As noted above, embedding involving the separateapplication of the additives 222 can be referred as two-step embedding.Subsequently, the resulting host material 224 has at least some of theadditives 222 partially or fully embedded into the surface of the hostmaterial 224. Optionally, suitable processing can be carried out toconvert the dry composition 226 into the host material 224, such as byadditional drying, curing, cross-linking, polymerization, or anycombination thereof. Any, or all, of the manufacturing stagesillustrated in FIG. 2C can be carried out in the presence of a vaporenvironment of a suitable fluid (e.g., an embedding fluid or othersuitable fluid) to facilitate the embedding of the additives 222, toslow drying of the wet composition 218, or both.

Certain aspects regarding the application of the additives 222 and theembedding fluid 228 and the embedding of the additives 222 on theright-side of FIG. 2C can be carried out using similar processingconditions and materials as described above for FIG. 2A and FIG. 2B, andthose aspects need not be repeated below. In particular, and in at leastcertain aspects, the processing conditions for embedding the additives222 into the dry composition 226 on the right-side of FIG. 2C can beviewed as largely parallel to those used when embedding the additives212 into the dry composition 208 of FIG. 2B.

In the case of a patterned transparent conductor, surface embeddingaccording to FIG. 2C can be carried out generally uniformly across thewet composition 218 or the dry composition 226, followed by spatiallyselective or varying treatment to yield higher conductance and lowerconductance portions across the host material 224. Alternatively, or inconjunction, surface embedding according to FIG. 2C can be carried outin a spatially selective or varying manner, such as by disposing orforming the wet composition 218 in a spatially selective or varyingmanner over the substrate 220, by applying the additives 222 in aspatially selective or varying manner across either, or both, of the wetcomposition 218 and the substrate 220, by applying the additives 222 ina spatially selective or varying manner across either, or both, of thedry composition 226 and the substrate 220, by applying the embeddingfluid 228 in a spatially selective or varying manner across either, orboth, of the dry composition 226 and the substrate 220, or anycombination thereof.

Patterning of Transparent Conductors

Patterned transparent conductors can be used in, for example, touchsensors, liquid crystal display (or LCD) pixel electrodes, and otherelectronic devices. Adequate electrical isolation between conductivetraces is desirable to isolate electrical signals to achieve spatialresolution in touch sensing or pixel switching. Adequate transparency ofthe transparent conductors is desirable to achieve higher displaybrightness, contrast ratio, image quality, and power consumptionefficiency, while adequate electrical conductivity is desirable tomaintain high signal to noise ratios, switching speeds, refresh rates,response time, and uniformity. For applications where electricalpatterning is desirable but optically (e.g., visible to the human eye)observable patterning is undesirable, adequate pattern invisibility orlow pattern visibility is desirable. Electrically isolated patternswhich are nearly or substantially indistinguishable by the human eye areparticularly desirable.

According to some embodiments, an electrically conductive pattern ofadditives can be surface embedded into selected portion or portions of asubstrate or an unpatterned coating. For example, printing on thesubstrate or the coating can achieve patterning of a transparentconductor by surface embedding. Other spatially selective or varyingmanner of application of either, or both, additives and an embeddingfluid can be used. Examples of techniques useful for directly patterninga substrate or a coating include printing methods such as screen,ink-jet, aerosol-jet, ultrasonic spray, continuous deposition, gravure,intaglio, pad, roll, offset, mimeography, and imprint, and other methodssuch as using a mask.

In some embodiments, an embedding dispersion including additives and anembedding fluid that swells or softens a host material can be printedinto a pattern directly onto the host material. In some embodiments, theembedding dispersion is i) substantially free of binders or fillers, andii) includes volatile (e.g., alcohol) solvent(s). Binders and fillersthat negatively affect electrical and optical characteristics can beomitted, although the lack of binders and fillers may inhibit the use ofcertain printing techniques. Fillers can be included to make printingeasier by reducing settling and increasing viscosity. Certain fillersmay reduce conductivity to varying degrees, which can be advantageous(e.g., to form lower conductance portions that should be opticallysimilar to higher conductance portions), or can be omitted whereconductivity is desirable. Polymethyl methacrylate (or PMMA, MW of about1M) when used as a filler can increase viscosity and slow settling(e.g., 5× slower settle rate) without significantly hinderingperformance.

FIG. 3A illustrates a manufacturing method of a patterned transparentconductor 300, according to an embodiment of the invention. As shown inFIG. 3, an active substrate 302 can be provided. By “active,” it will beunderstood that the substrate 302 is sufficiently affected by, or isotherwise sufficiently susceptible to, an embedding fluid to permitsurface embedding of additives in the presence of the embedding fluid,whether or not the resulting surface-embedded additives form a networkthat is electrically conductive. “Active” can be contrasted with“inactive” for which surface embedding does not occur (or is otherwiseinhibited). It will also be understood that “active” can be relative toa particular embedding fluid, such that the substrate 302 (or other hostmaterial) can be active relative to one embedding fluid, but inactiverelative to another embedding fluid.

Next, additives 304 and an embedding fluid (not shown) can be applied tothe substrate 302 in a spatially selective or varying manner, such as byprinting or another technique. The additives 304 can be electricallyconductive or semiconducting, such as in the form of nanowires,nanotubes, or other nano-sized or micron-sized structures having anaspect ratio of about 3 or greater. The additives 304 can be in solutionor otherwise dispersed in the embedding fluid, and can be simultaneouslyapplied to the substrate 302 via one-step embedding. Alternatively, theadditives 304 can be separately applied to the substrate 302 before,during, or after the embedding fluid treats the substrate 302. As notedabove, the separate application of the additives 304 and the embeddingfluid can be referred as two-step embedding. In the case of two-stepembedding, the additives 304 can be applied in a spatially selective orvarying manner, while the embedding fluid can be applied uniformly ornon-uniformly across the substrate 302. Subsequently, the resultingpatterned transparent conductor 300 has at least some of the additives304 partially or fully embedded into a surface of the substrate 302, andarranged according to a pattern to form higher conductance portions 306.Gaps between the higher conductance portions 306 are substantiallydevoid of the additives 304 and form lower conductance portions 308. Itwill be understood that “lower conductance” or “lower sheet conductance”can encompass an insulating nature in an absolute sense, but need notnecessarily refer to such absolute sense. Rather, “lower-conductance”more generally can refer to a portion that is sufficiently insulatingfor purposes of electrical isolation, or can be relative to anotherportion having a higher sheet conductance. In some embodiments, anelectrical contrast between the portions 306 and 308 can be such that asurface or sheet resistance of the lower conductance portions 308 can beat least about 2 times a sheet resistance of the higher conductanceportions 306, such as at least about 5 times, at least about 10 times,at least about 20 times, at least about 50 times, at least about 100times, at least about 500 times, at least about 1,000 times, or at leastabout 10,000 times, and up to about 100,000 times, up to about 1,000,000times, or more. In some embodiments, a surface or sheet resistance ofthe lower conductance portions 308 can be at least about 100 Ω/sq, suchas at least about 200 Ω/sq, at least about 500 Ω/sq, at least about1,000 Ω/sq, at least about 10,000 Ω/sq, or at least about 100,000 Ω/sq,and up to about 1,000,000 Ω/sq, up to about 10,000,000 Ω/sq, or more.

A similar sequence of operations as set forth in FIG. 3A can be carriedout on surfaces on different sides of the substrate 302, therebyresulting in multiple-sided (e.g., two-sided) patterning. FIG. 3Billustrates a patterned transparent conductor 314 similar to thepatterned transparent conductor 300 of FIG. 3A, but also havingadditives 316 partially or fully embedded into an opposite, bottomsurface of the substrate 302, and arranged according to a pattern toform higher conductance portions 310 and lower conductance portions 312.The additives 304 and 316 can be the same or different. A top patterncan substantially overlie a bottom pattern, or, as shown in FIG. 3B, thetop pattern can be offset or arranged in a staggered manner relative tothe bottom pattern, such that the higher conductance portions 306 canoverlie the lower conductance portions 312, and the lower conductanceportions 308 can overlie the higher conductance portions 310. Thisoffset arrangement can achieve low visibility of the top and bottompatterns. Other arrangements of the top and bottom patterns arecontemplated, such as in a cross-wise manner.

FIG. 4 illustrates a manufacturing method of a patterned transparentconductor 400, according to another embodiment of the invention. Asshown in FIG. 4, a substrate 402 can be provided, where the substrate402 can be either active or inactive, and an active, unpatterned coating404 is applied on top of the substrate 402. Next, additives 406 and anembedding fluid (not shown) can be applied to the coating 404 in aspatially selective or varying manner via one-step embedding or two-stepembedding, such as by printing or another technique. In the case oftwo-step embedding, the additives 406 can be applied in a spatiallyselective or varying manner, while the embedding fluid can be applieduniformly or non-uniformly across the coating 404. Subsequently, theresulting patterned transparent conductor 400 has at least some of theadditives 406 partially or fully embedded into a surface of the coating404, and arranged according to a pattern to form higher conductanceportions 408. Gaps between the higher conductance portions 408 aresubstantially devoid of the additives 406 and form lower conductanceportions 410. A similar sequence of operations as set forth in FIG. 4can be carried out on surfaces on different sides of the patternedtransparent conductor 400, thereby resulting in multiple-sided (e.g.,two-sided) patterning. Certain aspects of the method of FIG. 4 and thepatterned transparent conductor 400 can be similarly implemented asdescribed above for FIG. 3, and those aspects are repeated.

Other embodiments for direct patterning are contemplated. For example,to reduce an optical contrast between higher conductance and lowerconductance portions, a material can be disposed or included in thelower conductance portions to sufficiently match optical characteristicsof surface-embedded additives in the higher conductance portions. Insuch manner, the higher and lower conductance portions can yield lowvisibility patterning, while an electrical contrast is maintainedbetween the higher and lower conductance portions. By sufficientlymatching optical characteristics of the higher and lower conductanceportions, these portions can be rendered substantially visuallyindistinguishable or undetectable to the human eye. The extent to whicha patterning of the higher and lower conductance portions is visuallyindistinguishable can be evaluated, for example, across a group ofnormally sighted human subjects (e.g., in the young to middle adult agerange) and under photopic conditions. In some embodiments, thepatterning of the higher and lower conductance portions can be deemedsubstantially visually indistinguishable if the patterning is undetectedby at least about 90% of the human subjects, such as at least about 93%,at least about 95%, at least about 97%, at least about 98%, at leastabout 99%, or more.

For example, lower conductance portions can include additives that donot readily form a percolating network, but have optical characteristics(e.g., haze, transmittance, absorbance, and reflectance) that closelymatch optical characteristics of a percolating network in higherconductance portions of a patterned transparent conductor. Examples ofadditives for the lower conductance portions include nanoparticles (orother spheroidal structures having an aspect ratio less than about 3)formed of non-conductive or lower-conductivity materials, or nanowires(or other elongated structures) that form a non-percolating networkbecause of nanowire geometry or because of surface treatment. Examplesof surface treatments for reducing or degrading electricallyconductivity of otherwise conductive nanowires include silane-basedmaterials such as vinyl triethoxysilane and aminopropyl triethoxysilane.

In some embodiments, a difference in transmittance values (e.g.,absolute difference between transmittance values each expressed as apercentage) of the higher and lower conductance portions can be nogreater than about 10%, such as no greater than about 5%, no greaterthan about 4%, no greater than about 3%, no greater than about 2%, nogreater than 1%, or no greater than 0.5%, and down to about 0.1%, downto about 0.01%, down to about 0.001%, or less, where the transmittancevalues can be expressed in terms of human vision or photometric-weightedtransmittance, transmittance at a given wavelength or range ofwavelengths in the visible range, such as about 550 nm, solar-fluxweighted transmittance, transmittance at a given wavelength or range ofwavelengths in the infrared range, or transmittance at a givenwavelength or range of wavelengths in the ultraviolet range. In someembodiments, a difference in haze values (e.g., absolute differencebetween haze values each expressed as a percentage) of the higher andlower conductance portions can be no greater than about 5%, such as nogreater than about 4%, no greater than about 3%, no greater than about2%, no greater than about 1%, no greater than 0.5%, or no greater than0.1%, and down to about 0.05%, down to about 0.01%, down to about0.001%, or less, where the haze values can be expressed as human visionor photometric-weighted haze, haze at a given wavelength or range ofwavelengths in the visible range, such as about 550 nm, solar-fluxweighted haze, haze at a given wavelength or range of wavelengths in theinfrared range, or haze at a given wavelength or range of wavelengths inthe ultraviolet range. In some embodiments, a difference in absorbancevalues (e.g., absolute difference between absorbance values eachexpressed as a percentage) of the higher and lower conductance portionscan be no greater than about 10%, such as no greater than about 5%, nogreater than about 4%, no greater than about 3%, no greater than about2%, no greater than 1%, or no greater than 0.5%, and down to about 0.1%,down to about 0.01%, down to about 0.001%, or less, where the absorbancevalues can be expressed as human vision or photometric-weightedabsorbance, absorbance at a given wavelength or range of wavelengths inthe visible range, such as about 550 nm, solar-flux weighted absorbance,absorbance at a given wavelength or range of wavelengths in the infraredrange, or absorbance at a given wavelength or range of wavelengths inthe ultraviolet range. In some embodiments, a difference in reflectancevalues (e.g., absolute difference between diffuse reflectance valueseach expressed as a percentage) of the higher and lower conductanceportions can be no greater than about 10%, such as no greater than about5%, no greater than about 4%, no greater than about 3%, no greater thanabout 2%, no greater than 1%, or no greater than 0.5%, and down to about0.1%, down to about 0.01%, down to about 0.001%, or less, where thereflectance values can be expressed as human vision orphotometric-weighted reflectance, reflectance at a given wavelength orrange of wavelengths in the visible range, such as about 550 nm,solar-flux weighted reflectance, reflectance at a given wavelength orrange of wavelengths in the infrared range, or reflectance at a givenwavelength or range of wavelengths in the ultraviolet range.

For example, using a surface embedding formulation targeted to asubstrate or a coating, nanowires (or another conductive orsemiconductive additive) can be printed and embedded where conductivityis desired, and a non-conductive filler can be printed and embeddedwhere conductivity is not desired. Reversing this order of embedding isalso contemplated. In this example, the filler can render the conductivenanowire pattern to be substantially invisible, by matching opticalcharacteristics of the nanowires while remaining non-conductive. Inplace of, or in conjunction with, the non-conductive filler, nanowires(or another conductive or semiconductive additive) that are bulkincorporated in a suitable coating material can be printed whereconductivity is not desired. Bulk incorporation inhibits junctionformation of nanowires for reduced conductivity, while the presence ofthe non-conductive, bulk incorporated nanowires can match opticalcharacteristics of the conductive embedded nanowires.

As another example, using a surface embedding formulation targeted to asubstrate or a coating, nanowires (or another conductive orsemiconductive additive) can be printed and embedded where conductivityis desired. Using another formulation that still allows embedding butinhibits conductivity, nanowires (or another conductive orsemiconductive additive) can be printed and embedded where conductivityis not desired. For example, the latter formulation can include a binderor filler that disrupts junction formation between nanowires, or caninhibit junction formation by promoting deep embedding of the nanowiresbelow a surface. Reversing this order of embedding is also contemplated.In this example, the presence of nanowires in both the higherconductance and lower conductance regions can render the conductivenanowire pattern to be substantially invisible, because the lowerconductance embedded nanowires match optical characteristics of thehigher conductance embedded nanowires while remaining non-conductive. Insome embodiments, a loading level of nanowires in the lower conductanceportions can be at least about 1/20 of a loading level of nanowires inthe higher conductance portions, such as at least about 1/10, at leastabout ⅕, at least about ½, at least about 6/10, at least about 7/10, atleast about 8/10, or at least about 9/10, and up to, or somewhat greaterthan, the loading level in the higher conductance portions.

As another example, using a surface embedding formulation targeted to asubstrate or a coating, a non-conductive filler can be coated andembedded substantially uniformly, and then, using the same or adifferent surface embedding formulation, nanowires (or anotherconductive or semiconductive additive) can be printed and embedded whereconductivity is desired. Reversing this order of embedding is alsocontemplated. Here, the resulting conductive nanowire pattern can remainvisible to some extent, although the presence of non-conductive fillerin gaps between or interspersed within the pattern can reduce an opticalcontrast between higher and lower conductance portions by avoiding alarge step-like optical transition between the portions. Furtherimprovements in optical contrast can be achieved by smoothing theoptical transition away from a step-like transition, such as accordingto a horizontal or lateral gradient profile.

As another example, using a surface embedding formulation targeted to asubstrate or a coating, nanowires (or another conductive orsemiconductive additive) can be coated and embedded substantiallyuniformly at a loading level below the percolation threshold. Then,using the same or a different surface embedding formulation, additionalnanowires (or another conductive or semiconductive additive) can beprinted and embedded in portions where conductivity is desired, yieldinga combined loading level of nanowires above the percolation threshold inthose portions. Reversing this order of embedding is also contemplated.Here, the resulting conductive nanowire pattern can remain visible tosome extent, although the presence of nanowires in gaps between orinterspersed within the pattern can reduce an optical contrast betweenhigher and lower conductance portions by avoiding a large step-likeoptical transition between the portions. Further improvements in opticalcontrast can be achieved by smoothing the optical transition away from astep-like transition, such as according to a horizontal or lateralgradient profile.

As another example, using a formulation that still allows embedding in asubstrate or a coating but inhibits conductivity, nanowires (or anotherconductive or semiconductive additive) can be coated and embeddedsubstantially uniformly at a loading level below the percolationthreshold. Then, using a surface embedding formulation targeted to thesubstrate or the coating, nanowires (or another conductive orsemiconductive additive) can be printed and embedded in portions whereconductivity is desired, yielding a combined loading level of nanowiresabove the percolation threshold in those portions. Reversing this orderof embedding is also contemplated. Here, the resulting conductivenanowire pattern can remain visible to some extent, although thepresence of nanowires in gaps between or interspersed within the patterncan reduce an optical contrast between higher and lower conductanceportions by avoiding a large step-like optical transition between theportions. Further improvements in optical contrast can be achieved bysmoothing the optical transition away from a step-like transition, suchas according to a horizontal or lateral gradient profile.

As a further example, instead of printing, a physical mask, a patternedphotoresist layer, or other type of mask can be placed adjacent to asurface of a substrate or a coating. The mask has a pattern that coversselected portion or portions of the surface while leaving other portionsuncovered. A dispersion including additives and an embedding solventthat swells or softens the surface is applied onto the covered anduncovered portions. Additives are embedded into portions that are leftunmasked to form higher conductance portions whereas additives are notembedded (or inhibited from embedding) into portions that are covered bythe mask, thereby leaving these latter portions of lower conductance.The mask can be bonded to the underlying surface, such as by anadhesive, to inhibit the embedding dispersion from penetratingunderneath the mask. The physical mask also can be applied underpressure onto the surface for the aforementioned purpose. The mask canbe flat or can be in the form of a roller.

According to some embodiments, patterning of transparent conductors canbe carried out without relying on printing of additives or otherspatially selective application of additives to a host material. Asnoted above, binders and fillers used in certain printing techniquessometimes can negatively affect electrical and optical characteristicsof resulting embedded additives, such as by inhibiting formation of apercolating network. Advantageously, some embodiments can achievepatterning through a substantially uniform application of additives to ahost material, thereby decoupling the application of additives frombinders and fillers used in certain printing techniques.

In some embodiments, patterning of transparent conductors can be carriedout by applying a spatially selective or varying treatment to inhibitpercolation over portion or portions where electrical conductivity isnot desired. In physical inhibition of percolation, additives embeddedin lower conductance portions are physically or otherwise treated toinhibit effective contact with one another to form a percolatingnetwork, whereas additives embedded in higher conductance portions cancontact one another, resulting in a percolating network over the higherconductance portions. Physical inhibition of percolation can involvephysically degrading junctions between additives, physically degradingthe additives themselves, such as through partial or complete removal,or both, and can be accomplished by subtractive processes, such as laserablation, corona arc discharge, milling, or any combination thereof. Inchemical inhibition of percolation, additives embedded in lowerconductance portions are exposed to a chemical agent or otherwisechemically treated to inhibit or inactivate electron conduction acrossdifferent additives in a network. Chemical inhibition of percolation caninvolve chemically degrading junctions between additives, chemicallydegrading the additives themselves, such as by dissolving the additivesor converting the additives into structures with higher resistivity, orboth, and can be accomplished by subtractive processes, such asoxidation or sulfidation, by introducing insulating molecular ligandsbetween the additives to inhibit electron conduction across junctions,or any combination thereof. It will be understood that theclassification of “physical” and “chemical” inhibition of percolation isfor ease of presentation, and that certain treatments can inhibitpercolation through a combination of physical and chemical degradationof electrical conductivity.

In some embodiments, embedded additives can be selectively removed. Forexample, a laser can be rastered over a surface with embedded additivesto ablate away additives in a spatially selective or varying manner,forming lower conductance portion or portions. Ablation can be partialor full. For example, a dispersion including additives and an embeddingsolvent can be applied substantially uniformly over a surface of asubstrate or a coating, thereby swelling or softening the surface toembed the additives into the surface. Selected portion or portions ofthe surface with unpatterned, embedded additives can be ablated to forma pattern of higher and lower conductance portions. For applications forwhich low visibility or invisibility of patterns is desired, partiallaser ablation can be performed, so as to electrically pattern thematerials with reduced optical contrast. Advantageously, althoughadditives can be ablated sufficiently to render them electricallyisolated in the lower conductance portions, the resulting patterns arelargely or substantially indistinguishable or undetectable.

In some embodiments, a patterned transparent conductor can be formedthrough spatially selective or varying application of an etchant, suchas through a mask or by printing. Etching can be partial or full. Forexample, an unpatterned transparent conductor can be formed by embeddingnanowires into a surface of a substrate or a coating. Selected portionsof the surface can be masked, and the resulting masked surface can besubjected to a selective chemical etch to remove additives from unmaskedportions, forming lower conductance portions. Masked portions of thesurface are protected from etching by the mask and remain conductive.For applications for which low visibility or invisibility of patterns isdesired, an etchant can have the effect of degrading or reducingelectrical conductivity of additives in etched portions, but leaving theetched portions largely or substantially optically unchanged as viewedby the human eye. This effect can be attained, for example, by partiallydegrading the additives, by disrupting junctions between the additives,or both. A rinsing operation can be employed to remove the etchant, butcan also be used to neutralize the etchant during the rinse, so as notto damage parts of the surface which are intended to remain un-etched.

An etchant can be an acid, a base, or a largely neutral solution (e.g.,a pH in the range of about 5.5 to about 8.5 or about 5.5 to about 7encompassing weak acids and weak bases), and can be in a liquid state, agaseous state, or a both. Examples of etchants include oxidants, whichcan refer to a variety of materials that remove electrons from anotherreactant in a redox chemical reaction. In the case of silver nanowiresor other types of conductive or semiconductive additives, a variety ofoxidants, which react with silver (or another material forming theadditives) can be used, such as oxygen, ozone, hydrogen peroxide,inorganic peroxide, polyether oxide, hypochlorite, hypohalite compounds,and so forth. In the case of hydrogen peroxide, chemical etching ofsilver-containing additives can proceed according to the followingreaction scheme: 2Ag+H₂O₂→Ag₂O+H₂O. In the case of printing, a printableetchant (e.g., a screen-printable etchant) can be water-based (i.e.,aqueous) and can be formulated based on hydrogen peroxide (or anotheroxidant or combination of oxidants), along with one or more of (1) aviscosity enhancer or aid for printing, (2) a surfactant or a wettingagent, and (3) an anti-foaming or anti-bubbling agent. Since bothhydrogen peroxide and water are high surface tension liquids, theformulation can be designed to allow uniform printing over a hydrophobicsurface, which allows uniform degrading of electrical conductivity overselected portions of the surface. Chemical etching can be partial orfull by, for example, adjusting the formulation of an etchant (e.g.,acidity or type of oxidant), adjusting the application conditions (e.g.,exposure duration to the etchant), or both.

FIG. 5 illustrates a manufacturing method of a patterned transparentconductor 500, according to an embodiment of the invention. As shown inFIG. 5, an active substrate 502 is provided. Next, additives 504 and anembedding fluid (not shown) can be applied to the substrate 502 in asubstantially uniform manner via one-step embedding or two-stepembedding, resulting in the additives 504 becoming partially or fullyembedded into a surface of the substrate 502. Then, an etchant 506 canbe applied to the substrate 502 with the surface-embedded additives 504in a spatially selective or varying manner, such as by screen printingor through the use of a mask. In this embodiment, the etchant 506 isapplied so as to largely or substantially remove additives 504 overportions exposed to the etchant 506, forming lower conductance portions510. Portions that are not exposed to the etchant 506 remain conductive,forming higher conductance portions 508. Optionally, a cleaning orrinsing operation can be carried out to remove any remaining etchant506. In place of, or in conjunction with, etching, another subtractiveprocess can be used, such as laser ablation, corona arc discharge,milling, or a combination thereof. Certain aspects of the method of FIG.5 and the patterned transparent conductor 500 can be similarlyimplemented as described above for FIG. 3 through FIG. 4, and thoseaspects are repeated.

FIG. 6 illustrates a manufacturing method of a patterned transparentconductor 600, according to another embodiment of the invention. Asshown in FIG. 6, a substrate 602 can be provided, where the substrate602 can be either active or inactive, and an active, unpatterned coating604 is applied on top of the substrate 602. Next, additives 606 and anembedding fluid (not shown) can be applied to the coating 604 in asubstantially uniform manner via one-step embedding or two-stepembedding, resulting in the additives 606 becoming partially or fullyembedded into a surface of the coating 604. Then, an etchant 608 can beapplied to the coating 604 with the surface-embedded additives 606 in aspatially selective or varying manner, such as by screen printing orthrough the use of a mask. In this embodiment, the etchant 608 isapplied so as to largely or substantially remove additives 606 overportions exposed to the etchant 608, forming lower conductance portions612. Portions that are not exposed to the etchant 608 remain conductive,forming higher conductance portions 610. In place of, or in conjunctionwith, etching, another subtractive process can be used, such as laserablation, corona arc discharge, milling, or a combination thereof.Certain aspects of the method of FIG. 6 and the patterned transparentconductor 600 can be similarly implemented as described above for FIG. 3through FIG. 5, and those aspects are repeated.

FIG. 7 illustrates a manufacturing method of a patterned transparentconductor 700, according to an embodiment of the invention. As shown inFIG. 7, an active substrate 702 is provided. Next, additives 704 and anembedding fluid (not shown) can be applied to the substrate 702 in asubstantially uniform manner via one-step embedding or two-stepembedding, resulting in the additives 704 becoming partially or fullyembedded into a surface of the substrate 702. Then, an etchant 706 canbe applied to the substrate 702 with the surface-embedded additives 704in a spatially selective or varying manner, such as by screen printingor through the use of a mask. To obtain low visibility patterning, theetchant 706 is applied so as to partially remove or degrade additives704 over portions exposed to the etchant 706, forming lower conductanceportions 710. For example, additives 704 in the lower conductanceportions 710 can be etched sufficiently to render them electricallyisolated in the lower conductance portions 710, without fully etchingaway the additives 704 from those portions 710. Portions along thesubstrate 702 that are not exposed to the etchant 706 remain conductive,forming higher conductance portions 708. In place of, or in conjunctionwith, etching, another subtractive process can be used, such as laserablation, corona arc discharge, milling, or a combination thereof.Certain aspects of the method of FIG. 7 and the patterned transparentconductor 700 can be similarly implemented as described above for FIG. 3through FIG. 6, and those aspects are repeated.

FIG. 8 illustrates a manufacturing method of a patterned transparentconductor 800, according to another embodiment of the invention. Asshown in FIG. 8, an inactive substrate 802 can be provided, although thesubstrate 802 also can be active in another embodiment, and an active,unpatterned coating 804 is applied on top of the substrate 802. Next,additives 806 and an embedding fluid (not shown) can be applied to thecoating 804 in a substantially uniform manner via one-step embedding ortwo-step embedding, resulting in the additives 806 becoming partially orfully embedded into a surface of the coating 804. Then, an etchant 808can be applied to the coating 804 with the surface-embedded additives806 in a spatially selective or varying manner, such as by screenprinting or through the use of a mask. To obtain low visibilitypatterning, the etchant 808 is applied so as to partially remove ordegrade additives 806 over portions exposed to the etchant 808, forminglower conductance portions 812. For example, additives 806 in the lowerconductance portions 812 can be etched sufficiently to render themelectrically isolated in the lower conductance portions 812, withoutfully etching away the additives 806 from those portions 812. Portionsalong the coating 804 that are not exposed to the etchant 808 remainconductive, forming higher conductance portions 810. In place of, or inconjunction with, etching, another subtractive process can be used, suchas laser ablation, corona arc discharge, milling, or a combinationthereof. Certain aspects of the method of FIG. 8 and the patternedtransparent conductor 800 can be similarly implemented as describedabove for FIG. 3 through FIG. 7, and those aspects are repeated.

According to some embodiments, patterning of a transparent conductor canbe carried out by implementing an embedding depth offset across ahorizontal or laterally extending direction along the transparentconductor, such that different portions along the transparent conductorinclude conductive or semiconductive additives that are surface embeddedto varying extents. Typically, deeply embedding beneath a surface suchthat additives are enveloped and covered by a non-conductive hostmaterial can inhibit electrical conductivity across a network of theadditives, whereas embedding partially into the surface can enhancenetwork percolation and electrical conductivity. Also, little or noembedding, such as in the case of surface-deposited additives, caninhibit junction formation and result in reduced electricalconductivity. By adjusting or tuning embedding depth in a spatiallyvarying or selective manner across a transparent conductor, lowerconductance portions can be formed with additives deeply embedded into asurface or remaining on the surface, and higher conductance portions canbe formed in which the additives are partially embedded into a surface.

In some embodiments, a substrate or a coating can be converted in aspatially varying or selective manner to render certain portions more orless susceptible to surface embedding. Upon surface embedding, anembedding depth offset is obtained across the substrate or the coating,such that electrically conductive or semiconductive additives percolateand can carry current in some portions but not in other portions. Ingeneral, the process of conversion can include spatially selectiveapplication of an electromagnetic radiation (e.g., UV, microwaveradiation, or laser radiation), an electric field, ozone, a flametreatment, a chemical radical, a gas, a plasma treatment, a plasmaspray, a plasma oxidation, chemical reduction (e.g., a chemical reducingatmosphere), chemical oxidation (e.g., a chemical oxidizing atmosphere),vapor, a chemical precursor, an acid, a base, a cross-linking agent, anetchant, or any combination thereof. Because additives can be present inboth higher and lower conductance portions at substantially the same orsimilar loading levels (albeit with different depths of embedding), thehigher conductance portions can be largely or substantiallyindistinguishable from the lower conductance portions. For example, anembedding solvent, corona treatment, UV ozone treatment, or depositionof a material can be carried out on certain portions of a substrate or acoating to render those portions more susceptible to embedding, therebypromoting a larger extent of embedding such that additives in thoseportions do not form a percolation network.

Spatial patterning of higher and lower conductance portions of anadditive network can involve the use of a physical mask, a photomask, astencil, or the like, which can be positioned in front of a conversionsource, in front of a substrate or a coating, in contact with thesubstrate or the coating, or on a reverse side of the substrate or thecoating opposite to the conversion source.

In some embodiments, conversion of a substrate or a coating can occurbefore deposition of additives. In such embodiments, selected spatialportions of the substrate or the coating can be converted to control thedegree of embedding or to control the morphology of an additive networksuch that converted portions allow electron conduction whereas untreatedportions do not allow electron conduction (or allow conduction to a lowdegree). Alternatively, selected portions of the substrate or thecoating can be converted to spatially control the degree of embedding orthe morphology of an additive network such that converted portions donot allow electron conduction (or allow conduction to a low degree)whereas untreated portions allow electron conduction.

In other embodiments, conversion of a substrate or a coating can occurafter deposition of additives. In such embodiments, additives can besurface-deposited in a substantially uniform manner over the substrateor the coating. Next, surface embedding can be performed by printing anembedding fluid over portions where conductivity is desired. Theembedding fluid promotes embedding of the additives to permit contactand percolation between the additives. Alternatively, or in conjunction,surface embedding can be performed by printing an embedding fluid overportions where conductivity is not desired. The embedding fluid promotesembedding of the additives to inhibit contact and percolation betweenthe additives, such as by over-embedding the additives beneath asurface, by over-coating the individual additives with an insulatingmaterial, or both. Another option involves surface depositing additivessubstantially uniformly over a substrate or a coating, and then convertselected portions where conductivity is desired. The conversion itselfcan impart conductivity, or can be followed with an embedding fluidtreatment (e.g., liquid or vapor) or heat treatment. Yet another optioninvolves surface depositing additives substantially uniformly over asubstrate or a coating, and then convert selected portions whereconductivity is not desired. The conversion can degrade or reduceconductivity by itself, or can be followed by another suitable treatmentfor such purpose.

FIG. 9 illustrates a cross section of a patterned transparent conductor900 including additives 902 that are embedded to varying depths into anembedding surface S of a host material 912, according to an embodimentof the invention. Additives 902 in one portion 910 are surfaceconductive and are partially embedded into the embedding surface S andpartially exposed at the embedding surface S. Additives 902 in anadjacent portion 911 are more deeply embedded beneath the surface S andare rendered non-conductive. As shown in FIG. 9, the additives 902 inthe higher conductance portion 910 are localized within an embeddedregion 920 of the host material 912, and the embedded region 920 isrelatively thin and is adjacent to the embedding surface S. Theadditives 902 in the lower conductance portion 911 are localized withinan embedded region 922 of the host material 912, and the embedded region922 is relatively thick and is below and spaced apart from the embeddingsurface S. A thickness of the embedded region 922 can be at least about1.1 times a thickness of the embedded region 920, such as at least about1.2 times, at least about 1.5 times, at least about 2 times, at leastabout 2.5 times, or at least about 3 times, and up to about 5 times, upto about 10 times, or more. A surface coverage of the additives 902 inthe higher conductance portion 910 can be at least about 25%, such as atleast about 30%, at least about 40%, at least about 50%, at least about60%, or at least about 75%, and up to about 90%, up to about 95%, or upto about 100%, while a surface coverage of the additives 902 in thelower conductance portion 911 can be below 25%, such as up to about 20%,up to about 15%, up to about 10%, up to about 5%, or up to about 3%, anddown to about 2%, down to about 1%, or up to about 0%. Although FIG. 9illustrates embedding depth offset, it is also contemplated that theadditives 902 in the higher and lower conductance portions 910 and 911can be embedded to the same or similar depth relative to the embeddingsurface S, but subjected to chemical or other inhibition of percolationas explained above.

A variety of techniques can be used for forming transparent conductorsvia embedding depth offset. FIG. 10 illustrates a roll-to-roll techniquethat uses corona treatment, according to an embodiment of the invention.In FIG. 10, a roll-to-roll corona treatment device 1000 includes acorona electrode 1001, which can be connected to a high voltagegenerator (not shown). The corona electrode 1001 is mounted in a spacedrelationship to a ground electrode 1004 that acts as a roller conveyinga film web 1003. A capacitance is induced between the corona electrode1001 and the ground electrode 1004. A stencil or mask 1002 is placedbetween the two electrodes 1001 and 1004 to allow selective coronatreatment of a surface of the web 1003 with a high voltage arc dischargefrom a corona or plasma induced between the electrodes 1001 and 1004. Astencil pattern can be any arbitrary pattern along a longitudinaldirection of the film web 1003, a transverse direction, or any othergeometry. The stencil 1002 can be located at various distances betweenthe corona electrode 1001 and the film web 1003 with air or anotherdielectric material in between. The stencil 1002 can be formed of anysuitable material that can effectively mask off certain portions forwhich corona treatment is not desired. Ozone, oxidants, or otherchemical agents also can be introduced facilitate surface treatment. Thestencil 1002 can be moving or stationary. In place of, or in conjunctionwith, embedding depth offset, the roll-to-roll corona treatment device1000 can be used to obtain patterning via physical or chemicalinhibition of percolation.

FIG. 11 illustrates a roll-to-roll technique similar to that shown inFIG. 10, in which a stencil or mask 1105 is in the form of a roller thathouses the corona electrode 1001, or is otherwise disposed between thecorona electrode 1001 and the surface of the film web 1003. In anotherembodiment, illustrated in FIG. 12, a stencil or mask 1206 is locatedbehind the film web 1003 and between the film web 1003 and the groundelectrode 1004. The stencil 1206 in this embodiment can be formed of anelectrically conductive material to attract corona arc discharges. Thecorona arc discharges can selectively treat portions of the film web1003 directly above patterned conductors on a roller below.

FIG. 13 illustrates a manufacturing method of a patterned transparentconductor 1300, according to an embodiment of the invention. As shown inFIG. 13, an active substrate 1302 can be provided. Next, an over-activeinducing agent 1304 can be applied to the substrate 1302 in a spatiallyselective or varying manner, such as by screen printing or through theuse of a mask. By “over-active inducing,” it will be understood thatagent 1304 affects or renders the substrate 1302 susceptible to anextent of embedding that inhibits junction formation and electricalpercolation, such as by over-embedding beneath a surface of thesubstrate 1302. For example, in the case of a polycarbonate film orsheet as the substrate 1302, the over-active inducing agent 1304 caninclude cyclohexanone or another embedding fluid having a high solvencyfor the substrate 1302. Optionally, a cleaning or rinsing operation canbe carried out to remove any remaining over-active inducing agent 1304.Then, additives 1306 and an embedding fluid (not shown) can be appliedto the substrate 1302 in a substantially uniform manner via one-stepembedding or two-step embedding, resulting in higher conductanceportions 1308 with the partially embedded additives 1306 and lowerconductance portions 1310 with the over-embedded additives 1306. Certainaspects of the method of FIG. 13 and the patterned transparent conductor1300 can be similarly implemented as described above for FIG. 3 throughFIG. 12, and those aspects are repeated. Another embodiment can beimplemented in a similar manner as shown in FIG. 13, in which theprocessing operations are carried out over an active coating that is ontop of a substrate, which can be either active or inactive.

FIG. 14 illustrates a manufacturing method of a patterned transparentconductor 1400, according to an embodiment of the invention. As shown inFIG. 14, an active substrate 1402 can be provided. Next, the substrate1402 is treated in a spatially selective or varying manner, such asusing plasma, corona, or UV ozone treatment, to render over-activecertain portions of the substrate. By “over-active,” it will beunderstood that the spatially selective treatment affects or renders thesubstrate 1402 susceptible to an extent of embedding that inhibitsjunction formation and electrical percolation, such as by over-embeddingbeneath a surface of the substrate 1402. The spatially selectivetreatment can be carried out through the use of a mask 1404. Then,additives 1406 and an embedding fluid (not shown) can be applied to thesubstrate 1402 in a substantially uniform manner via one-step embeddingor two-step embedding, resulting in higher conductance portions 1408with the partially embedded additives 1406 and lower conductanceportions 1410 with the over-embedded additives 1406. Certain aspects ofthe method of FIG. 14 and the patterned transparent conductor 1400 canbe similarly implemented as described above for FIG. 3 through FIG. 13,and those aspects are repeated. Another embodiment can be implemented ina similar manner as shown in FIG. 14, in which the processing operationsare carried out over an active coating that is on top of a substrate,which can be either active or inactive.

FIG. 15 illustrates a manufacturing method of a patterned transparentconductor 1500, according to an embodiment of the invention. As shown inFIG. 15, an active substrate 1502 can be provided. Next, a patternedover-active layer 1504 can be formed on the substrate 1502 in aspatially selective or varying manner, such as by printing or throughthe use of a mask. By “over-active,” it will be understood that thelayer 1504 is sufficiently affected by, or is otherwise sufficientlysusceptible to, an embedding fluid to permit an extent of embedding thatinhibits junction formation and electrical percolation, such as byover-embedding beneath a surface of the substrate 1502. It will also beunderstood that “over-active” can be relative to a particular embeddingfluid, such that the layer 1504 (or other host material) can beover-active relative to one embedding fluid, but active or inactiverelative to another embedding fluid. For example, in the case of apolycarbonate film or sheet as the substrate 1502, the over-active layer1504 can be a layer of polymethyl methacrylate that has greatersolubility in, or lesser solvent resistance towards, a particularembedding fluid. Then, additives 1506 and an embedding fluid (not shown)can be applied to the substrate 1502 and the over-active layer 1504 in asubstantially uniform manner via one-step embedding or two-stepembedding, resulting in higher conductance portions 1508 with theadditives 1506 partially embedded into the substrate 1502 and lowerconductance portions 1510 with the additives 1506 over-embedded into thelayer 1504. Certain aspects of the method of FIG. 15 and the patternedtransparent conductor 1500 can be similarly implemented as describedabove for FIG. 3 through FIG. 14, and those aspects are repeated.Another embodiment can be implemented in a similar manner as shown inFIG. 15, in which the processing operations are carried out over anactive coating that is on top of a substrate, which can be either activeor inactive.

FIG. 16 illustrates a manufacturing method of a patterned transparentconductor 1600, according to an embodiment of the invention. As shown inFIG. 16, an active substrate 1602 can be provided. Next, a patternedinactive layer 1604 can be formed on the substrate 1602 in a spatiallyselective or varying manner, such as by printing or through the use of amask. By “inactive,” it will be understood that the layer 1604 issufficiently unaffected by, or is otherwise immune to, an embeddingfluid such that little or no surface embedding occurs in the layer 1604.It will also be understood that “inactive” can be relative to aparticular embedding fluid, such that the layer 1604 (or other hostmaterial) can be inactive relative to one embedding fluid, but active orover-active relative to another embedding fluid. To obtain lowvisibility patterning, the layer 1604 includes nanoparticles, fillers,or another material dispersed therein for optical matching, such asliquid crystal materials, photochromic materials (e.g., silver halidesfor glass substrates or organic photochromic molecules such as oxazines,or naphthopyrans for polymer substrates). Then, additives 1606 and anembedding fluid (not shown) can be applied to the substrate 1602 and theinactive layer 1604 in a substantially uniform manner via one-stepembedding or two-step embedding, resulting in higher conductanceportions 1608 with the additives 1606 partially embedded into thesubstrate 1602 and lower conductance portions 1610 with the additives1606 surface-deposited on the layer 1604. Optionally, a cleaning orrinsing operation can be carried out to remove the surface-depositedadditives 1606, although at least some of the surface-depositedadditives 1606 can be retained to tune an extent of optical matchingbetween the higher and lower conductance portions 1608 and 1610. Certainaspects of the method of FIG. 16 and the patterned transparent conductor1600 can be similarly implemented as described above for FIG. 3 throughFIG. 15, and those aspects are repeated. Another embodiment can beimplemented in a similar manner as shown in FIG. 16, in which theprocessing operations are carried out over an active coating that is ontop of a substrate, which can be either active or inactive.

FIG. 17 illustrates a manufacturing method of a patterned transparentconductor 1700, according to an embodiment of the invention. As shown inFIG. 17, an active substrate 1702 can be provided. Next, a de-activatingagent 1704 can be applied to the substrate 1702 in a spatially selectiveor varying manner, such as by screen printing or through the use of amask. By “de-activating,” it will be understood that the agent 1704affects or renders the substrate 1702 sufficiently immune to anembedding fluid such that little or no surface embedding occurs overportions of the substrate 1702 exposed to the agent 1704. For example,the de-activating agent 1704 can include a cross-linking agent, whichcan be applied along with UV or heat treatment to cross-link certainportions of the substrate 1702 to inhibit surface embedding. As anotherexample, the de-activating agent 1704 can include a de-wetting agent toinhibit wetting by an embedding fluid. Optionally, a cleaning or rinsingoperation can be carried out to remove any remaining de-activating agent1704. Then, additives 1706 and an embedding fluid (not shown) can beapplied to the substrate 1702 in a substantially uniform manner viaone-step embedding or two-step embedding, resulting in higherconductance portions 1708 with the additives 1706 partially embeddedinto the substrate 1702 and lower conductance portions 1710 with theadditives 1706 surface-deposited on the substrate 1702. Optionally, acleaning or rinsing operation can be carried out to remove thesurface-deposited additives 1706, although at least some of thesurface-deposited additives 1706 can be retained for optical matchingbetween the higher and lower conductance portions 1708 and 1710. Certainaspects of the method of FIG. 17 and the patterned transparent conductor1700 can be similarly implemented as described above for FIG. 3 throughFIG. 16, and those aspects are repeated. Another embodiment can beimplemented in a similar manner as shown in FIG. 17, in which theprocessing operations are carried out over an active coating that is ontop of a substrate, which can be either active or inactive.

FIG. 18 illustrates a manufacturing method of a patterned transparentconductor 1800, according to an embodiment of the invention. As shown inFIG. 18, an active substrate 1802 can be provided. Next, a patternedinactive layer 1804 can be formed on the substrate 1802 in a spatiallyselective or varying manner, such as by printing or through the use of amask. Then, additives 1806 and an embedding fluid (not shown) can beapplied to the substrate 1802 and the inactive layer 1804 in asubstantially uniform manner via one-step embedding or two-stepembedding, resulting in higher conductance portions 1808 with theadditives 1806 partially embedded into the substrate 1802 and lowerconductance portions 1810 with the additives 1806 surface-deposited onthe layer 1804. Optionally, a cleaning or rinsing operation can becarried out to remove the surface-deposited additives 1806, although atleast some of the surface-deposited additives 1806 can be retained foroptical matching between the higher and lower conductance portions 1808and 1810. Certain aspects of the method of FIG. 18 and the patternedtransparent conductor 1800 can be similarly implemented as describedabove for FIG. 3 through FIG. 17, and those aspects are repeated.Another embodiment can be implemented in a similar manner as shown inFIG. 18, in which the processing operations are carried out over anactive coating that is on top of a substrate, which can be either activeor inactive.

FIG. 19 illustrates a manufacturing method of a patterned transparentconductor 1900, according to an embodiment of the invention. As shown inFIG. 19, an inactive substrate 1902 can be provided. Next, a patternedactive layer 1904 can be formed on the substrate 1902 in a spatiallyselective or varying manner, such as by printing or through the use of amask. For example, in the case the substrate 1902 is formed of glass ora polymer having a high degree of crystallinity or cross-linking (e.g.,polyethylene terephthalate), the active layer 1904 can be a layer ofpolymethyl methacrylate that has greater solubility in, or lessersolvent resistance towards, a particular embedding fluid. Then,additives 1906 and an embedding fluid (not shown) can be applied to thesubstrate 1902 and the active layer 1904 in a substantially uniformmanner via one-step embedding or two-step embedding, resulting in higherconductance portions 1908 with the additives 1906 partially embeddedinto the layer 1904 and lower conductance portions 1910 with theadditives 1906 surface-deposited on the substrate 1902. Optionally, acleaning or rinsing operation can be carried out to remove thesurface-deposited additives 1906, although at least some of thesurface-deposited additives 1906 can be retained for optical matchingbetween the higher and lower conductance portions 1908 and 1910. Certainaspects of the method of FIG. 19 and the patterned transparent conductor1900 can be similarly implemented as described above for FIG. 3 throughFIG. 18, and those aspects are repeated. Another embodiment can beimplemented in a similar manner as shown in FIG. 19, in which theprocessing operations are carried out over an inactive coating that ison top of a substrate, which can be either active or inactive.

FIG. 20 illustrates a manufacturing method of a patterned transparentconductor 2000, according to an embodiment of the invention. As shown inFIG. 20, an inactive substrate 2002 can be provided. Next, anunpatterned active coating 2004 can be formed on the substrate 2002. Forexample, in the case the substrate 2002 is formed of glass or a polymerhaving a high degree of crystallinity or cross-linking, the activecoating 2004 can be a coating of polymethyl methacrylate that hasgreater solubility in, or lesser solvent resistance towards, aparticular embedding fluid. Next, a de-activating agent 2006 can beapplied to the coating 2004 in a spatially selective or varying manner,such as by screen printing or through the use of a mask. For example,the de-activating agent 2006 can include a cross-linking agent, whichcan be applied along with UV or heat treatment to cross-link certainportions of the coating 2004 to inhibit surface embedding. As anotherexample, the de-activating agent 2006 can include a de-wetting agent toinhibit wetting by an embedding fluid. Optionally, a cleaning or rinsingoperation can be carried out to remove any remaining de-activating agent2006. Then, additives 2008 and an embedding fluid (not shown) can beapplied to the coating 2004 in a substantially uniform manner viaone-step embedding or two-step embedding, resulting in higherconductance portions 2010 with the additives 2008 partially embeddedinto the coating 2004 and lower conductance portions 2012 with theadditives 2008 surface-deposited on the coating 2004. Optionally, acleaning or rinsing operation can be carried out to remove thesurface-deposited additives 2008, although at least some of thesurface-deposited additives 2008 can be retained for optical matchingbetween the higher and lower conductance portions 2010 and 2012. Certainaspects of the method of FIG. 20 and the patterned transparent conductor2000 can be similarly implemented as described above for FIG. 3 throughFIG. 19, and those aspects are repeated. Another embodiment can beimplemented in a similar manner as shown in FIG. 20, in which theprocessing operations are carried out over an inactive coating that ison top of a substrate, which can be either active or inactive.

FIG. 21 illustrates a manufacturing method of a patterned transparentconductor 2100, according to an embodiment of the invention. As shown inFIG. 21, an inactive substrate 2102 can be provided. Next, anunpatterned active coating 2104 can be formed on the substrate 2102.Next, a de-activating agent 2106 can be surface embedded into thecoating 2104 in a spatially selective or varying manner, such as byprinting or through the use of a mask. For example, the de-activatingagent 2006 can include a cross-linking agent, which can be surfaceembedded along with nanoparticles, fillers, or another material foroptical matching and low visibility patterning. Next, UV or heattreatment can be applied to cross-link certain portions of the coating2104 to inhibit surface embedding. Then, additives 2108 and an embeddingfluid (not shown) can be applied to the coating 2104 in a substantiallyuniform manner via one-step embedding or two-step embedding, resultingin higher conductance portions 2110 with the additives 2108 partiallyembedded into the coating 2104 and lower conductance portions 2112 withthe additives 2108 surface-deposited on the coating 2104. Optionally, acleaning or rinsing operation can be carried out to remove thesurface-deposited additives 2108, although at least some of thesurface-deposited additives 2108 can be retained to tune an extent ofoptical matching between the higher and lower conductance portions 2110and 2112. Certain aspects of the method of FIG. 21 and the patternedtransparent conductor 2100 can be similarly implemented as describedabove for FIG. 3 through FIG. 20, and those aspects are repeated.Another embodiment can be implemented in a similar manner as shown inFIG. 21, in which the processing operations are carried out over aninactive coating that is on top of a substrate, which can be eitheractive or inactive.

Various options of a generalized manufacturing method of a patternedtransparent conductor are illustrated in FIG. 22A through FIG. 22C,according to embodiments of the invention. It is noted that certainstages in the method are optional, and each stage can be implemented ina number of different ways. Thus, various possible permutations of themethod are illustrated in FIG. 22A through FIG. 22C, all of which arewithin the scope of embodiments herein.

Referring to FIG. 22A, the transparent conductor is formed starting froma substrate, as indicated in stage 0. The substrate can be active orinactive. For some embodiments (e.g., inverse patterning), both activeand inactive substrate types can be used. In some embodiments,processing can be carried out regardless of the substrate type.

In stage 1, which is optional, the substrate can be coated in asubstantially uniform manner with an active or inactive layer (e.g., apolymer layer or sub-layer), a cross-linking agent, a combination of anactive layer and an etchant, or a material that can be referred as a“wildcard” material, such as one included for optical matching. Wildcardmaterials can include materials other than nanoparticles and nanowiresthat afford substantially the same or similar optical characteristics assilver nanowires. Examples of wildcard materials include liquid crystalmaterials or photochromic materials (e.g., silver halides for glasssubstrates or organic photochromic molecules such as oxazines ornaphthopyrans for polymer substrates). Where the substrate is coatedwith an active or inactive layer, a combination of substrate and thelayer is sometimes referred to as a “base”.

In stage 2, the base can undergo an optional spatially selectivechemical, physical, or other morphological conversion. Examples of suchconversion include exposure of the base to a directed plasma source,depositing a cross-linking agent in a spatially selective mannerfollowed by curing, or masking followed by broad exposure to a plasmasource or a cross-linking agent. It is noted that the order ofimplementation of stages 1 and 2 can be reversed in some embodiments.

In stage 3, a patterned surface optionally can be formed, such as bymasking or printing. The surface can be patterned by printing an activeor inactive polymer. In some cases, the polymer that is printed caninclude bulk incorporated nanoparticles, nanowires, or other additives.In other cases, the polymer that is printed can include bulkincorporated nanoparticles, nanowires, or other additives, and can becured. Curing can include cross-linking of a polymer (e.g., after addinga cross-linking agent or based on the formulation of an original polymerresin) as well as other hardening resulting in a substantially permanentconfiguration. In other cases, a substrate or a layer can be patternedby printing a solvent that is capable of softening or swelling amaterial of the substrate or the layer. In other cases, a pattern can beformed by printing nanowires from a solvent. In still other cases, thesurface can be patterned by printing an etchant. The etchant candeactivate electrical conductivity of a nanowire network while largelyor substantially retaining optical characteristics of the nanowirenetwork. An etchant can be implemented chemically, such as by wetchemistry or vapor chemistry. Another subtractive process, such asscribing or milling with a laser, corona discharge, and the like, alsocan be used in place of, or in conjunction with, chemical etching.

Referring next to FIG. 22B, the method can proceed to optional stage 4,in which a polymer, nanowires, or nanoparticles can be applied in aspatially selective manner (e.g., printed or doctor filled) to form aninverse pattern. In inverse printing of a polymer, a polymer of a typeopposite to that printed in a previous stage can be printed in spaces orgaps between portions of the previously printed polymer. For example, ifan active polymer pattern is printed in stage 3, an inactive polymerpattern can be printed in spaces between the active polymer pattern instage 4. Alternatively, if an inactive polymer pattern is printed instage 3, an active polymer pattern can be printed in spaces between theinactive polymer pattern in stage 4. Similarly, if a pattern ofnanowires is printed in stage 3, nanoparticles can be inversely printedin spaces between the nanowire pattern in stage 4. Alternatively, if apattern of nanoparticles is printed in stage 3, nanowires can beinversely printed in spaces between the nanoparticle pattern in stage 4.

In an optional stage 5, any exposed active materials can be pre-swelledby exposing them to a solvent.

In stage 6, the substrate or the layer can be coated in a substantiallyuniform manner with nanowires. The nanowires can be coated by dispersingthem in a solvent, and then coating the substrate or the layer with thenanowire-containing solvent. The substrate or the layer can be inactive,active, or over-active relative to the solvent. In some embodiments, thecoating of the nanowires can be doctor filled. It is noted that, in someembodiments, stage 6 can be performed before stage 5, or before stage 4.After coating, an optional mask can be disposed over the coatedsubstrate or the coated layer in stage 7.

Additional patterning optionally can be performed in stage 8, such as byetching across the entire surface, by patterned etching (e.g., byprinting of an etchant), or by printing of a cross-linking agent. Asnoted above, an etchant can be implemented chemically, such as by wetchemistry or vapor chemistry. Another subtractive process also can beused, such as scribing or milling with a laser, corona discharge, andthe like.

An optional rinsing or washing stage 8.5 can be implemented at thispoint to remove any undesired or un-embedded nanoparticles or nanowires.

In stage 9, additional nanowires or nanoparticles optionally can beapplied to selected portions of the surface (e.g., inactive portions),such as for the purpose of optical matching.

In stage 10, either of, or both, nanoparticles and nanowires can besurface embedded into active portions of the surface. The particularportions into which nanowires or nanoparticles are embedded depend onthe previous process stages. In general, nanowires or nanoparticles canbe embedded into active portions, but with little or no embedding intoinactive portions. The embedding at stage 10 can involve exposure of theentire surface to solvent vapor or by coating the surface with asolvent, if a solvent has not been applied previously. The embeddingoptionally can involve curing of active portions including nanoparticlesor nanowires, such as by application of light, heat, and so forth. Theembedding also optionally can involve pressure rolling with a patternedimprinting roller, an uniform roller, or a combination of both types ofrollers. In addition, a pattern of a solvent can be selectively printedover the surface, where the surface is active relative to the solvent.

After stage 10 and referring next to FIG. 22C, an optional partialetching stage 11 can be implemented. In place of, or in conjunction withstage 11, an optional stage 12 can involve overcoating or overprintingthe surface to insulate or protect exposed nanowires, such as using apolymer.

FIG. 23A through FIG. 23F illustrate examples of patterned transparentconductors 2300, 2302, 2304, 2306, 2308, and 2310 formed according tothe method of FIG. 22A through FIG. 22C, according to embodiments of theinvention. It is noted that the patterned transparent conductors 2300,2302, 2304, 2306, 2308, and 2310 are provided by way of example, andthat a number of other configurations can be obtained by the methodsdescribed above, including those set forth in FIG. 22A through FIG. 22C.

As shown in FIG. 23A, the patterned transparent conductor 2300 includesa first set of additives 2312 that are surface-embedded into one portionof an active substrate 2314 to form a higher conductance portion 2316,and a second set of additives 2318 that are surface-embedded intoanother portion of the active substrate 2314 to form a lower conductanceportion 2320. For example, the additives 2312 can include nanowires,nanotubes, or other elongated structures having an aspect ratio of about3 or more, while the additives 2318 can include nanoparticles or otherspheroidal structures having an aspect ratio less than about 3. Asanother example, the additives 2312 can be partially embedded into asurface of the substrate 2314, while the additives 2318 can be moredeeply embedded below the surface of the substrate 2314. As a furtherexample, the additives 2318 can be partially etched or otherwise treatedto degrade or reduce the electrically conductivity of the lowerconductance portion 2320. The higher conductance portion 2316 and thelower conductance portion 2320 can have optical characteristics that arelargely or substantially matching for low visibility patterning.

As shown in FIG. 23B, the patterned transparent conductor 2302 includesa first set of additives 2322 that are surface-embedded into one portionof a substrate 2324 to form a higher conductance portion 2326, and asecond set of additives 2328 that are surface-deposited (with little orno embedding) on another portion of the substrate 2324 to form a lowerconductance portion 2330. The additives 2322 and the additives 2328 canbe the same or different, and the higher conductance portion 2326 andthe lower conductance portion 2330 can have optical characteristics thatare largely or substantially matching for low visibility patterning.

As shown in FIG. 23C, the patterned transparent conductor 2304 includesan active layer 2332 that is disposed on top of a substrate 2334, whichcan be either active or inactive. The layer 2332 can be formed as acoating of a polymer, for example. A first set of additives 2336 aresurface-embedded into one portion of the layer 2332 to form a higherconductance portion 2338, and a second set of additives 2340 aresurface-embedded into another portion of the layer 2332 to form a lowerconductance portion 2342. For example, the additives 2336 can includenanowires, nanotubes, or other elongated structures having an aspectratio of about 3 or more, while the additives 2340 can includenanoparticles or other spheroidal structures having an aspect ratio lessthan about 3. As another example, the additives 2336 can be partiallyembedded into a surface of the layer 2332, while the additives 2340 canbe more deeply embedded below the surface of the layer 2332. As afurther example, the additives 2340 can be partially etched or otherwisetreated to degrade or reduce the electrically conductivity of the lowerconductance portion 2342. The higher conductance portion 2338 and thelower conductance portion 2342 can have optical characteristics that arelargely or substantially matching for low visibility patterning.

As shown in FIG. 23D, the patterned transparent conductor 2306 includesa first active layer 2342 that is disposed on top of a substrate 2344,which can be either active or inactive, as well as a second active layer2346 that is disposed on top of the substrate 2344 and is laterallyadjacent to the first active layer 2342. The first layer 2342 can be apatterned layer of a host material that permits surface embedding in amanner that promotes the formation of a percolating network, while thesecond layer 2346 can be a patterned layer of a different host materialthat permits surface embedding in a manner that inhibits the formationof a percolating network. Examples of suitable materials for the firstlayer 2342 include acrylics (e.g., polymethyl methacrylate),polycarbonates, polyimides, and the like, and examples of suitablematerials for the second layer 2346 include ceramics (e.g., asilane-based material), certain forms of acrylics, and the like. A firstset of additives 2348 are surface-embedded into the first layer 2342 toform a higher conductance portion 2352, and a second set of additives2350 are surface-embedded into the second layer 2346 to form a lowerconductance portion 2354. The additives 2348 and the additives 2350 canbe the same or different, and the higher conductance portion 2352 andthe lower conductance portion 2354 can have optical characteristics thatare largely or substantially matching for low visibility patterning.

As shown in FIG. 23E, the patterned transparent conductor 2308 includesan active layer 2356 that is disposed on top of a substrate 2358. Thelayer 2356 can be a patterned layer of a host material that is appliedin a spatially selective manner to cover certain areas of the substrate2358, while remaining areas of the substrate 2358 remain uncovered bythe layer 2356. A first set of additives 2360 are surface-embedded intothe layer 2356 to form a higher conductance portion 2362, and a secondset of additives 2364 are surface-deposited (with little or noembedding) on uncovered or exposed areas of the substrate 2358 to form alower conductance portion 2366. An overcoat 2368 can be applied in aspatially selective manner over the surface-deposited additives 2364 toretain the additives 2364 and to planarize a surface of the patternedtransparent conductor 2308. The overcoat 2368 also can be omitted asshown for the patterned transparent conductor 2310 of FIG. 23F, in whicha thickness or an amount of the surface-deposited additives 2364 isadjusted to planarize the surface. The additives 2360 and the additives2364 can be the same or different, and the higher conductance portion2362 and the lower conductance portion 2366 can have opticalcharacteristics that are largely or substantially matching for lowvisibility patterning.

Devices Including Transparent Conductors

The transparent conductors described herein can be used as transparentconductive electrodes in a variety of devices. Examples of suitabledevices include solar cells (e.g., thin-film solar cells and crystallinesilicon solar cells), display devices (e.g., flat panel displays, liquidcrystal displays (“LCDs”), plasma displays, organic light emitting diode(“OLED”) displays, electronic-paper (“e-paper”), quantum dot displays(e.g., QLED Displays), and flexible displays), solid-state lightingdevices (e.g., OLED lighting devices), touch sensor devices (e.g.,projected capacitive touch sensor devices, touch-on-glass sensordevices, touch-on-lens projected capacitive touch sensor devices,on-cell or in-cell projected capacitive touch sensor devices, selfcapacitive touch sensor devices, surface capacitive touch sensordevices, and resistive touch sensor devices), smart windows (or otherwindows), windshields, aerospace transparencies, electromagneticinterference shields, charge dissipation shields, and anti-staticshields, as well as other electronic, optical, optoelectronic, quantum,photovoltaic, and plasmonic devices. The transparent conductors can betuned or optimized depending on the particular application, such as workfunction matching in the context of photovoltaic devices or tuning ofthe transparent conductors to form Ohmic contacts with other devicecomponents or layers.

In some embodiments, the transparent conductors can be used aselectrodes in touch screen devices. A touch screen device is typicallyimplemented as an interactive input device integrated with a display,which allows a user to provide inputs by contacting a touch screen. Thetouch screen is typically transparent to allow light and images totransmit through the device.

FIG. 24 illustrates an example of a projected capacitive touch screendevice 2400 according to an embodiment of the invention. The touchscreen device 2400 includes a thin-film separator 2404 that is disposedbetween a pair of patterned transparent conductive electrodes 2402 and2406, as well as a rigid touch screen 2408 that is disposed adjacent toa top surface of the transparent conductive electrode 2406. A change incapacitance occurs when a user contacts the touch screen 2408, and acontroller (not illustrated) senses the change and resolves a coordinateof the user contact. Advantageously, either, or both, of the transparentconductive electrodes 2402 and 2406 can be implemented using thetransparent conductors described herein. It is also contemplated thatthe transparent conductors can be included in resistive touch screendevices (e.g., 4-wire, 5-wire, and 8-wire resistive touch screendevices), which include a flexible touch screen and operate based onelectrical contact between a pair of transparent conductive electrodeswhen a user presses the flexible touch screen.

EXAMPLES

The following examples describe specific aspects of some embodiments ofthe invention to illustrate and provide a description for those ofordinary skill in the art. The examples should not be construed aslimiting the invention, as the examples merely provide specificmethodology useful in understanding and practicing some embodiments ofthe invention.

Example 1 Nanowire Dispersion

In one implementation, a first population of nanowires (having a firstset of morphological characteristics) is combined in solution with asecond population of nanowires (having a second set of morphologicalcharacteristics), and then surface-embedded in one operation. Forexample, the first population can include nanowires of about 20 nm indiameter (on average) and about 20 μm in length (on average), and thesecond population can include larger-sized nanowires of about 100 nm indiameter (on average) and about 100 μm in length (on average). The firstpopulation and the second population are mixed in about 40% (by volume)trifluoroethanol and about 60% (by volume) isopropanol, and thenslot-die coated onto a polyimide layer on a glass substrate. Eachnanowire population is included at a concentration of about 2 mg/ml, anda resulting surface-embedded structure exhibits about 92% intransmittance and about 100 Ohms/sq in sheet resistance.

In another implementation, a first population of nanowires (having afirst set of morphological characteristics) is initiallysurface-embedded into a host material, and then a second population ofnanowires (having a second set of morphological characteristics) issubsequently surface-embedded into the same region of the host material.The host material can be a coating, a substrate, or otherwise serve as amatrix for the surface-embedded nanowires. For example, one populationof nanowires can include nanowires of about 40 nm in diameter (onaverage) and about 20 μm in length (on average), and the otherpopulation of nanowires can include larger-sized nanowires of about 200nm in diameter (on average) and about 200 μm in length (on average).Each population of nanowires is dispersed in about 40% (by volume)trifluoroethanol and about 60% (by volume) isopropanol at aconcentration of about 2 mg/ml, and then sequentially slot-die coatedonto a polyimide layer on a glass substrate. A resultingsurface-embedded structure exhibits about 92% in transmittance and about100 Ohms/sq in sheet resistance.

Example 2 Formation of Patterned Transparent Conductor

A polydimethylsiloxane stamp is laser etched to form a patterned stamp,and the patterned stamp is used to stamp onto a reservoir of silvernanowires in a solution of about 50% (by volume) isopropanol and about50% (by volume) trifluoroethanol at a concentration of about 5 mg/ml.The patterned stamp is stamped onto a polyimide planarization layer ofabout 1 μm in thickness. The polyimide layer, which can be patterned orunpatterned, is disposed on a color filter. A bottom surface of thestamp can be the main or sole point of contact between the stamp and thepolyimide layer, while other patterned portions away from the bottomface of the stamp can make little or no contact with the polyimidelayer. In such manner, the pattern of the bottom surface of the stampcan be effectively transferred onto the polyimide layer. The alcoholsolution facilitates durable and spatially varying surface-embedding ofsilver nanowires into the polyimide layer according to the transferredpattern. The stamping process is desirably carried out in a manner suchthat at least a portion of the alcohol solution remains duringsurface-embedding. The stamp can be reused, such as by re-immersing orre-stamping onto the silver nanowire dispersion to transfer anotherpattern. The stamp can take on the form factor of a roller, similar to arotogravure used in intaglio printing. In other implementations, thestamp can be formed of another polymer, an elastomer, a metal, aceramic, or another suitable material.

Example 3 Formation of Patterned Transparent Conductor

A similar stamping process is carried out as set forth in Example 2,except where a stamp's bottom surface and top surface (which is recessedfrom the bottom surface as patterned by laser etching) are both wettedby a nanowire dispersion. Nanowires exposed on the bottom surface of thestamp are wiped off, leaving nanowires on the top surface. The stamp isapplied onto a polyimide substrate, and nanowires are surface-embeddedin regions according to the pattern of the top surface of the stamp.

Example 4 Formation of Patterned Transparent Conductor

A laser or another light source is used to crosslink or otherwise renderinactive certain portions of a PMMA photoresist, a polymer, or anotherhost material deposited on a cyclic olefin copolymer substrate. Forexample, a laser beam can be rastered across the polymer to form aninverse pattern. Then, a silver nanowire dispersion employing about 10%or more (by volume) trifluoroethanol in isopropanol can be slot-diecoated across the polymer. Silver nanowires deposited over inactiveportions of the polymer are inhibited against surface-embedding, whilesilver nanowires deposited over non-crosslinked portions aresurface-embedded. Then, a washing operation optionally can be used toselectively remove silver nanowires from the inactive portions that wererendered insoluble to the embedding solution, leaving nanowires that aresurface-embedded into temporarily solubilized portions of the polymer.Alternatively, the surface can be left unwashed so that the inactiveportions (with nanowires remaining on the surface) have reducedconductivity but blend in optically with nearby portions (withsurface-embedded nanowires) that have higher conductivity.

Example 5 Formation of Patterned Transparent Conductor

A similar patterning process is carried out as set forth in Example 4,except where a photolithographic mask is used to selectively exposecertain portions of a photoresist to UV light. Regardless of whether thephotoresist is positive or negative, the photolithographic maskingprocess forms solubilized portions of the photoresist to be developedand etched away, leaving remaining portions with durablysurface-embedded nanowires.

Example 6 Formation of Patterned Transparent Conductor

A chemical agent is used to crosslink or otherwise render inactivecertain portions of a photoresist, a polymer, or another host materialdeposited on a glass substrate. For example, the chemical agent can beprinted across the polymer to form an inverse pattern using any printingtechnique, such as screen printing, gravure printing, offset printing,and so forth. Then, a silver nanowire dispersion employing about 10% ormore (by volume) trifluoroethanol in isopropanol can be slot-die coatedacross the polymer. Then, a rinsing or washing operation optionally canbe used to selectively remove silver nanowires from the inactiveportions that were rendered insoluble to the embedding solution, leavingnanowires that are surface-embedded into temporarily solubilizedportions of the polymer. Alternatively, the surface can be left unwashedso that the inactive portions (with nanowires remaining on the surface)have reduced conductivity but blend in optically with nearby portions(with surface-embedded nanowires) that have higher conductivity.

Example 7 Formation of Patterned Transparent Conductor

On a glass substrate overcoated with a polyimide planarization layer, aphysical mask is applied tightly either by pressure or using anadhesive. Then, a nanowire dispersion including an embedding solvent isapplied onto the masked layer via slot-die coating. Either before orafter the polyimide layer has dried, the mask is removed, leavingnanowires durably surface-embedded within unmasked portions of thelayer. If the mask is still wet during removal, the mask can be rinsedor immersed in a solution to collect any remaining nanowires into abath, which can be re-condensed via settling or centrifugation forsubsequent use. The physical mask can be formed of a metal, a polymer, aceramic, or another material that is substantially insoluble in theembedding solvent. In place of, or in conjunction with, polyimide,another polymer (e.g., polymethyl methacrylate) or host material thatcan be affected by an embedding solvent can be used.

Example 8 Formation of Patterned Transparent Conductor

Onto a glass substrate, a layer of polyimide is applied in a patternedfashion by any suitable method, such as gravure printing, intaglioprinting, ink-jet printing, lithography, imprint, screen printing, andso forth. Then, a nanowire embedding dispersion is applied using anycoating method, and nanowires are selectively surface-embedded into thepolyimide pattern. Specifically, nanowires deposited over the polyimidepattern are surface-embedded, while nanowires deposited over portions ofthe glass substrate without the polyimide pattern are inhibited againstsurface-embedding. In place of, or in conjunction with, polyimide,another polymer (e.g., polymethyl methacrylate) or host material thatcan be affected by an embedding solvent can be used.

Example 9 Formation of Patterned Transparent Conductor

Onto a glass substrate, a layer of polyimide is applied in a patternedfashion by any suitable method, such as gravure printing, intaglioprinting, ink-jet printing, lithography, imprint, screen printing, andso forth. Some portions of the patterned layer include polyimide of TypeA, while others portions include polyimide of Type B. Type A promoteshigher conductivity, while Type B promotes lower conductivity. Nanowirescan remain on a surface of the Type B portions, or can besurface-embedded into the Type B portions although exhibiting reducedconductivity. Then, a nanowire embedding dispersion is applied using anycoating method, and nanowires are selectively surface-embedded into thepolyimide pattern. In addition, portions of the pattern includingpolyimide of Type A exhibit high conductivity, while those portions ofthe pattern including polyimide of type B exhibit little or noconductivity. In place of, or in conjunction with, polyimide, anotherpolymer (e.g., polymethyl methacrylate) or host material that can beaffected by an embedding solvent can be used.

Example 10 Formation of Patterned Transparent Conductor

Onto a glass substrate, a layer of polyimide is applied in a firstpattern by any suitable method, such as gravure printing, intaglioprinting, ink-jet printing, lithography, imprint, screen printing, andso forth. Then, a nanowire embedding dispersion is applied using anycoating method, and nanowires are selectively surface-embedded into thefirst pattern. A second pattern in the inverse of the first pattern isthen printed, with a formulation that substantially optically matchesthe first pattern but electrically disables nanowires. In place of, orin conjunction with, polyimide, another polymer (e.g., polymethylmethacrylate) or host material that is susceptible to an embeddingsolvent can be used.

Example 11 Formation of Patterned Transparent Conductor

Onto a glass substrate, a layer of polyimide is applied in a firstpattern by any suitable method, such as gravure printing, intaglioprinting, ink-jet printing, lithography, imprint, screen printing, andso forth. A second pattern in the inverse of the first pattern is thenprinted so as to planarize the surface. The second pattern has aformulation that disables electrically conductivity of a nanowirenetwork. Then, a nanowire embedding dispersion is applied using anycoating method, resulting in the first pattern with surface-embeddednanowires exhibiting high conductivity, and the second pattern withsurface-embedded nanowires exhibiting little or no conductivity. Inplace of, or in conjunction with, polyimide, another polymer (e.g.,polymethyl methacrylate) or host material that can be affected by anembedding solvent can be used. Also, the second, inverse pattern caninclude a material that is not susceptible to the embedding solvent,thereby not permitting surface-embedding or permitting surface-embeddingto a low degree. A rinsing or washing operation optionally can be usedto selectively remove nanowires that are superficially deposited on thesecond, non-embedded pattern. The second, non-embedded pattern can havea formulation that substantially matches optical characteristics of thefirst pattern, such as one or more of transmittance, reflectance, haze,clarity, or another characteristic of the first pattern with thesurface-embedded nanowire network, thereby masking the patterns, hidingthe patterns, or rendering the patterns hard to detect visually oroptically.

Example 12 Formation of Patterned Transparent Conductor

An inverse pattern includes a material having one or more of absorbance,transmittance, reflectance, haze, or another optical characteristicmatched or similar to those of a surface-embedded silver nanowirenetwork. For example, if the silver nanowire network in surface-embeddedportions of a first polyimide pattern has a transmittance of about 90%,a haze of about 4%, an absorbance of about 1%, and a reflectance ofabout 9%, then a second, inverse pattern can include polyimideengineered to exhibit about 90% in transmittance, about 4% in haze,about 1% in absorbance, and about 9% in reflection. Methods ofengineering polyimide can include modifying its polymerization chemistryand compounding or embedding fillers into the polyimide, such as one ormore of scattering particles, absorbing particles, and reflectingparticles. In place of, or in conjunction with, polyimide, anotherpolymer (e.g., polymethyl methacrylate) or host material that can beaffected by an embedding solvent can be used.

Example 13 Formation of Patterned Transparent Conductor

Using a mimeograph, a glass substrate overcoated with a polyimide layeris surface-embedded with a dispersion of nanowires in ethanol andtrifluoroethanol. The dispersion is placed in a drum of a rotarymachine, such that when the substrate is pulled through the machine, therotating drum forces the dispersion through openings of a stencil. Thedesign of the stencil dictates a pattern of nanowires transferred ontothe polyimide layer. In place of, or in conjunction with, polyimide,another polymer (e.g., polymethyl methacrylate) or host material thatcan be affected by an embedding solvent can be used.

Example 14 Formation of Patterned Transparent Conductor

Areas over a substrate (where conductive traces are to be formed) areprinted with a host material that promotes higher conductivity, andremaining areas over the substrate (corresponding to gaps between theconductive traces) are printed with a different host material thatinhibits effective contact between nanowires, thereby creating lowerconductivity or insulating portions. For example, a silane-basedmaterial, such as tetraethoxysilane, can be printed over areas betweenthe conductive traces.

Example 15 Formation of Patterned Transparent Conductor

With a printing tool, positive portions of a pattern are printed in aspatially selective manner with conductive (e.g., silver) nanowires in asolution that surface-embeds the conductive nanowires into a substrateto form a percolating network. The negative portions of the pattern arethen printed with a silver-containing dispersion (e.g., silvernanoparticle dispersion) with a surface density or a concentration tosubstantially match optical characteristics of the positive, higherconductance portions, and the silver nanoparticles are similarlysurface-embedded into the substrate surface. This method yields higherconductance portions and lower conductance portions, yet matchingtransmission, reflection, scattering, and other optical characteristicsacross the two portions to a desirable degree. The patterning can beachieved by physical masking, shadow masking, a stencil, mimeograph,offset gravure, or any other printing method. The substrate can be aplastic film, a plastic sheet, a glass substrate, a glass substrateovercoated with a coating, or the like.

Example 16 Formation of Patterned Transparent Conductor

With a printing tool, positive portions of a pattern are printed in aspatially selective manner on a surface of a substrate with a polymersusceptible to surface-embedding. Negative portions of the pattern arenot printed and, therefore, correspond to uncovered portions of thesubstrate. Then, a nanowire embedding dispersion is applied using anycoating method, resulting in a surface-embedded conductive nanowirenetwork in positive portions of the pattern. The negative portions ofthe pattern can include nanowires that remain on the surface of thesubstrate, or the nanowires can be surface-embedded into the negativeportions although exhibiting reduced conductivity. Since nanowires arepresent in both the positive (higher conductance) and negative (lowerconductance) portions of the pattern, the resulting pattern is largelyinvisible. The functionality of the positive and negative portions ofthe pattern can be reversed, meaning that the positive portions of thepattern can be of lower conductance, and the negative portions of thepattern can be of higher conductance.

Example 17 Formation of Patterned Transparent Conductor

With a laser ablation tool, a substantially uniformly surface-embeddedsilver nanowire network adjacent to a surface of a substrate or anovercoat is ablated in a spatially selective manner to form lowerconductance regions. The ablation can be partial or full, resulting inabout 1-100% of silver nanowires adjacent to the surface ablated away totune an electrical contrast across the substrate. For example, partiallyablating about 50% of the nanowires from a portion can render thatportion insulating, whereas adjacent portions remain conductive, therebyachieving electrical isolation. This partial ablation also achieves lowoptical contrast between portions. Adjusting one or more of a power ofthe laser, a number of laser ablation passes, a speed of the laser, alaser pulse width, a concentration of the nanowires, a substratematerial, and other parameters can be used to control the extent ofablation.

Example 18 Formation of Patterned Transparent Conductor

Onto a glass substrate, a layer of polyimide is applied in a patternedfashion by any suitable method, such as gravure printing, intaglioprinting, ink-jet printing, lithography, imprint, screen printing, andso forth. Some portions of the patterned layer include polyimide of TypeA, while others portions include polyimide of Type B. Type A promoteshigher conductivity, while Type B promotes lower conductivity. A coronaor UV ozone treatment is then applied to either, or both, of the Type Aportions and the Type B portions with or without a photomask. The coronaor UV ozone treatment modifies the interaction of a nanowire dispersionwith the treated portions, such as by modifying their susceptibility tosurface-embedding. Then, a nanowire embedding dispersion is appliedusing any coating method, and nanowires are selectively surface-embeddedinto the polyimide pattern. In addition, portions of the patternincluding polyimide of Type A exhibit high conductivity, while thoseportions of the pattern including polyimide of type B exhibit little orno conductivity. In place of, or in conjunction with, polyimide, anotherpolymer (e.g., polymethyl methacrylate) or host material that can beaffected by an embedding solvent can be used.

Example 19 Formation of Patterned Transparent Conductor

A similar patterning process is carried out as set forth in Example 18,except that nanowires are initially applied without an embedding solventthat interacts with either the Type A portions or the Type B portions.Then in a subsequent operation, an embedding solvent is applied over thesubstrate and the polyimide pattern using a coating tool or viaembedding solvent vapor exposure.

Example 20 Formation of Patterned Transparent Conductor

A polycarbonate film (available under the trademark Lexan®) is maskedwith a conductive stencil, and then treated in an UV ozone chamber(UVOCS) for about 0.8 min. The film is then subjected to an applicationof a silver nanowire formulation of about 4 mg/ml concentration in about95% (by volume) isopropanol and about 5% (by volume) cyclohexanone. Thisformulation is deposited onto the polycarbonate film via a draw-downapplication of a rod coater with about 0.75 mil gap at a speed of about2 inches/second. The portions exposed to the UV ozone environment (i.e.,the unmasked portions) allow surface-embedding of silver nanowires in amanner that inhibits electrical percolation, such as by deeply embeddingthe nanowires beneath the surface of the polycarbonate. The maskedportions allow surface-embedding of silver nanowires in a manner thatpromotes electrical percolation. Resulting higher and lower conductanceportions exhibit little or no differences in optical characteristics(e.g., transmittance, haze, reflection, and absorption), thereby formingisolated conductive traces that are substantially visually undetectable.This example yields higher conductance portions of about 100 Ohms/sq andlower conductance portions of greater than about 100,000 Ohms/sq withsubstantially indistinguishable boundaries between the two portions.

Example 21 Formation of Patterned Transparent Conductor

A cyclic olefin copolymer (“COC”) film is initially treated with toluenevia a draw-down rod coater with about 2 mil gap and about 2 inch/secondlinear conveyance speed. After about 30 seconds to allow the toluene topartially evaporate, an application of silver nanowires in isopropanolis similarly drawn with the rod coater with about 1 mil gap and about 2inch/second linear conveyance speed. This renders the silver nanowiresdurably surface-embedded into the COC film, via a direct embeddingapproach and without requiring an overcoat. After the silver nanowiresare embedded uniformly in the COC film, the COC film is masked with aconductive stencil, exposing certain portions that are subjected to acorona arc discharge treatment. This treatment discharges electricityonto the exposed or unmasked portions, overloading current in thoseportions of a nanowire network and degrading junctions where theresistance is highest. In such manner, the exposed portions become lowerconductance portions, while preserving substantially matching opticalcharacteristics (e.g., transmittance, haze, reflection, and absorption)relative to masked portions that remain conductive.

Example 22 Formation of Patterned Transparent Conductor

A patterning process is carried out using a screen-printable etchantwith a formulation designed to degrade silver nanowire conductivity viapartial etching of surface-embedded silver nanowires. A polycarbonatesheet of about 180 μm in thickness is surface-embedded with silvernanowires to yield an optical transmission of about 90.6%, a haze ofabout 1.32%, and a surface resistivity of about 147 Ω/sq.

An aqueous screen-printable etchant is formulated based on (1) about5-20 vol % of hydrogen peroxide, (2) about 10-30 wt % hydroxyethylcellulose and about 0.1-5 wt % of polyethylene oxide as viscosityenhancers and aids for forming a printed film matrix, (3) about 0.01-1wt % of a silicon surfactant (available as BYK-348) and about 1-10% vol% of isopropanol or trifluoroethanol as surfactants or wetting agents,and (4) about 0.01-2 vol % of an anti-foaming or anti-bubbling agent(available as Rhodaline 646). Since both hydrogen peroxide and water arehigh surface tension liquids, the formulation is designed to allowuniform printing over a hydrophobic surface, which allows uniformdegrading of electrical conductivity over selected portions of thesurface. The screen-printable etchant is applied in a spatiallyselective manner over the polycarbonate sheet with surface-embeddednanowires, and then dried at room temperature or with moderate heat forabout 5-30 minutes and rinsed off using de-ionized water. The surfaceresistivity of the lower conductance portions became effectivelyinfinite while maintaining a similar transmission of about 92.1% and asimilar haze of about 1.26%.

FIG. 25A and FIG. 25B include microscope images illustrating atransparent conductor patterned using an aqueous screen-printableetchant, according to an embodiment of the invention. In FIG. 25A, apartially etched portion is on the left-hand side, and an un-etchedportion is on the right-hand side. In FIG. 25B (which is at a highermagnification than FIG. 25A), an un-etched portion is on the left-handside, and a partially etched portion is on the right-hand side. Thepartially etched and un-etched portions can be discerned at themagnifications shown in FIG. 25A and FIG. 25B, but are largely orsubstantially visually indistinguishable to the unaided human eye.

Example 23 Formation of Patterned Transparent Conductor

A polycarbonate sheet (available as Lexan® HP92S) with about 180 μm inthickness is used as a substrate. As a screen-printable over-activelayer, about 5-30 wt % of polystyrene, polystyrene-based copolymer,polymethyl methacrylate, polymethyl methacrylate-based copolymer (e.g.,polymethyl methacrylate-n-butyl methacrylate copolymer or polymethylmethacrylate-co-polylauryl methacrylate copolymer), polyethylmethacrylate, poly n-butyl methacrylate, polyisobutyl methacrylate,poly-n-butyl-polyisobutyl methacrylate copolymer, or a combinationthereof is dissolved in hexanol. The solution is screen printed in aspatially selective manner over areas of the substrate to result inlower conductance portions.

A dispersion of silver nanowires in about 0.1-10 vol % of cyclohexanonein isopropanol is prepared. The nanowires are about 40-80 nm in diameter(on average) and about 20-80 μm in length (on average). A concentrationof the nanowires is about 0.3-0.5 wt/vol % of the solvent mixture. Thenanowire dispersion is coated over the entire sample, such thatnanowires are surface-embedded into exposed portions of the substrate toachieve a surface resistance of about 10-500 Ω/sq, and nanowires aremore deeply embedded below a surface of the over-active layer to yieldan insulating surface. After surface-embedding, similar amounts ofsilver nanowires are embedded into higher and lower conductance portionsto yield similar transmission and haze values across the portions.

Example 24 Formation of Patterned Transparent Conductor

A polyethylene terephthalate (available as Melinex ST580) with about 76μm in thickness is used as a substrate. As a screen-printable activelayer, about 5-30 wt % of polystyrene, polystyrene-based copolymer,polymethyl methacrylate, polymethyl methacrylate-based copolymer (e.g.,polymethyl methacrylate-n-butyl methacrylate copolymer or polymethylmethacrylate-co-polylauryl methacrylate copolymer), or a combinationthereof is dissolved in anisole, cyclohexanone, methyl ethyl ketone, ormethyl isobutyl ketone. The solution is screen printed in a spatiallyselective manner over areas of the substrate to result in higherconductance portions.

A dispersion of silver nanowires in about 0.1-40 vol % oftrifluoroethanol, tetrafluoroethanol, dioxane, methyl isobutyl ketone,or cyclohexanone in isopropanol is prepared. The nanowires are about40-80 nm in diameter (on average) and about 20-80 μm in length (onaverage). A concentration of the nanowires is about 0.3-0.5 wt/vol % ofthe solvent mixture. The nanowire dispersion is coated over the entiresample, such that nanowires are surface-embedded into the active layerto achieve a surface resistance of about 10-500 Ω/sq, and nanowiresremain superficially deposited (with little or no embedding) on exposedportions of the substrate.

While the invention has been described with reference to the specificembodiments thereof, it should be understood by those skilled in the artthat various changes may be made and equivalents may be substitutedwithout departing from the true spirit and scope of the invention asdefined by the appended claims. In addition, many modifications may bemade to adapt a particular situation, material, composition of matter,method, or process to the objective, spirit and scope of the invention.All such modifications are intended to be within the scope of the claimsappended hereto. In particular, while the methods disclosed herein havebeen described with reference to particular operations performed in aparticular order, it will be understood that these operations may becombined, sub-divided, or re-ordered to form an equivalent methodwithout departing from the teachings of the invention. Accordingly,unless specifically indicated herein, the order and grouping of theoperations are not limitations of the invention.

What is claimed is:
 1. A patterned transparent conductor comprising: asubstrate; and additives at least partially embedded into at least onesurface of the substrate and localized adjacent to the surface accordingto a pattern to form higher sheet conductance portions, wherein thehigher sheet conductance portions are laterally adjacent to lower sheetconductance portions, wherein the higher sheet conductance portions areelectrically isolated from one another, wherein the patternedtransparent conductor further comprises a layer covering areas of thesurface corresponding to the lower sheet conductance portions.
 2. Thepatterned transparent conductor of claim 1, wherein a sheet resistanceof the lower sheet conductance portions is at least 100 times a sheetresistance of the higher sheet conductance portions.
 3. The patternedtransparent conductor of claim 1, wherein the additives form apercolating network within at least one of the higher sheet conductanceportions.
 4. The patterned transparent conductor of claim 1, wherein theadditives have an aspect ratio of at least
 3. 5. The patternedtransparent conductor of claim 1, wherein the lower sheet conductanceportions and the higher sheet conductance portions are substantiallyvisually indistinguishable.
 6. The patterned transparent conductor ofclaim 1, wherein a difference in transmittance values of the highersheet conductance portions and the lower sheet conductance portions isno greater than about 5%, and a difference in haze values of the highersheet conductance portions and the lower sheet conductance portions isno greater than about 5%.
 7. A patterned transparent conductorcomprising: a substrate; and additives at least partially embedded intoat least one surface of the substrate and localized adjacent to thesurface according to a pattern to form higher sheet conductanceportions, wherein the higher sheet conductance portions are laterallyadjacent to lower sheet conductance portions, wherein the additivescorrespond to first additives, and the patterned transparent conductorfurther comprises second additives included in the lower sheetconductance portions.
 8. The patterned transparent conductor of claim 7,wherein the second additives are embedded into the surface of thesubstrate within areas of the surface corresponding to the lower sheetconductance portions, and an extent of embedding of the second additiveswithin the lower sheet conductance portions is greater than an extent ofembedding of the first additives within the higher sheet conductanceportions.
 9. The patterned transparent conductor of claim 7, wherein thesecond additives are embedded into the surface of the substrate withinareas of the surface corresponding to the lower sheet conductanceportions, and the second additives are treated to inhibit formation of apercolating network.
 10. The patterned transparent conductor of claim 7,wherein the second additives are deposited on areas of the surface ofthe substrate corresponding to the lower sheet conductance portions. 11.The patterned transparent conductor of claim 7, wherein the patternedtransparent conductor further comprises a patterned layer covering areasof the surface corresponding to the lower sheet conductance portions,and the second additives are at least partially incorporated in thepatterned layer.
 12. A patterned transparent conductor comprising: asubstrate; and additives at least partially embedded into at least onesurface of the substrate and localized adjacent to the surface accordingto a pattern to form higher sheet conductance portions, wherein thehigher sheet conductance portions are laterally adjacent to lower sheetconductance portions, wherein the additives correspond to firstadditives, the surface corresponds to a first surface, and the patternedtransparent conductor further comprises second additives at leastpartially embedded into at least a second, opposite surface of thesubstrate.
 13. A touch screen device comprising the patternedtransparent conductor of claim
 1. 14. A patterned transparent conductorcomprising: a substrate; a coating disposed over at least one side ofthe substrate; and additives embedded into a surface of the coatingaccording to a pattern to form higher sheet conductance portions,wherein the additives are localized within a depth from the surface thatis less than a thickness of the coating, and the higher sheetconductance portions are spaced apart by gaps that correspond to lowersheet conductance portions, wherein substantially all of the additivesare localized within the depth from the surface that is no greater than75% of the thickness of the coating.
 15. The patterned transparentconductor of claim 14, wherein the additives include silver nanowires.16. The patterned transparent conductor of claim 14, wherein adifference in absorbance values of the higher sheet conductance portionsand the lower sheet conductance portions is no greater than about 5%.17. A patterned transparent conductor comprising: a substrate; a coatingdisposed over at least one side of the substrate; and additives embeddedinto a surface of the coating according to a pattern to form highersheet conductance portions, wherein the additives are localized within adepth from the surface that is less than a thickness of the coating, andthe higher sheet conductance portions are spaced apart by gaps thatcorrespond to lower sheet conductance portions, wherein the additivescorrespond to first additives, and the patterned transparent conductorfurther comprises second additives included in the lower sheetconductance portions.
 18. The patterned transparent conductor of claim17, wherein the second additives are embedded into the surface of thecoating within areas of the surface corresponding to the lower sheetconductance portions, and a surface coverage of the second additiveswithin the lower sheet conductance portions is less than a surfacecoverage of the first additives within the higher sheet conductanceportions.
 19. The patterned transparent conductor of claim 17, whereinthe second additives are embedded into the surface of the coating withinareas of the surface corresponding to the lower sheet conductanceportions, and the second additives are treated to inhibit formation of apercolating network.
 20. The patterned transparent conductor of claim17, wherein the second additives are deposited on areas of the surfaceof the coating corresponding to the lower sheet conductance portions.21. A touch screen device comprising the patterned transparent conductorof claim
 14. 22. A patterned transparent conductor comprising: asubstrate; a patterned layer covering an area of the substrate; andadditives embedded into a surface of the patterned layer to form ahigher sheet conductance portion, wherein the additives are localizedwithin a depth from the surface that is less than a thickness of thepatterned layer, and a laterally adjacent area of the substratecorresponds to a lower sheet conductance portion.
 23. The patternedtransparent conductor of claim 22, wherein a sheet resistance of thehigher sheet conductance portion is no greater than 500 Ω/sq, and asheet resistance of the lower sheet conductance portion is at least10,000 Ω/sq.
 24. The patterned transparent conductor of claim 22,wherein substantially all of the additives are localized within thedepth from the surface that is no greater than 50% of the thickness ofthe patterned layer.
 25. The patterned transparent conductor of claim22, wherein the additives correspond to first additives, and thepatterned transparent conductor further comprises second additivesincluded in the lower sheet conductance portion.
 26. The patternedtransparent conductor of claim 25, wherein the second additives aredeposited on the laterally adjacent area of the substrate.
 27. Thepatterned transparent conductor of claim 25, wherein the patterned layeris a first patterned layer, and the patterned transparent conductorfurther comprises a second patterned layer covering the laterallyadjacent area of the substrate, and the second additives are at leastpartially incorporated in the second patterned layer.
 28. The patternedtransparent conductor of claim 25, wherein the first additives have anaspect ratio of at least 3, and the second additives have an aspectratio less than
 3. 29. The patterned transparent conductor of claim 22,wherein a difference in reflectance values of the higher sheetconductance portion and the lower sheet conductance portion is nogreater than about 5%.
 30. A touch screen device comprising thepatterned transparent conductor of claim 22.